A transition path ensemble study reveals a linchpin role for Mg 2+ during rate-limiting ADP release from protein kinase A

Biochemistry

Volumn 48, Issue 48, 2009, Pages 11532-11545

  Khavrutskii, Ilja V ^a   Grant, Barry ^a   Taylor, Susan S ^a   McCammon, J Andrew ^a  

^a UNIVERSITY OF CALIFORNIA   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

ACTIVE SITE; BINDING AND RELEASE; ENSEMBLE TECHNIQUES; FOURIER; GROWTH AND DEVELOPMENT; HIGH AFFINITY; ION-BINDING; KEY REGULATORS; MONOVALENT CATIONS; PHOSPHORYL TRANSFER; PROTEIN KINASE; PROTEIN KINASE A; PROTEIN TARGETS; RATE LIMITING; SIGNALING NETWORKS; SUBSTRATE PROTEINS; TRANSITION PATHS;

BINDING ENERGY; BINDING SITES; BIOCHEMISTRY; PROTEINS; SIGNALING;

IONS;

ADENOSINE DIPHOSPHATE; CYCLIC AMP DEPENDENT PROTEIN KINASE; MAGNESIUM ION; PYROPHOSPHATE;

ARTICLE; BINDING AFFINITY; BINDING SITE; ENZYME ACTIVE SITE; ENZYME BINDING; ENZYME SUBSTRATE; PRIORITY JOURNAL;

ADENOSINE DIPHOSPHATE; ADENOSINE TRIPHOSPHATE; ALGORITHMS; BINDING SITES; CATIONS, DIVALENT; CYCLIC AMP-DEPENDENT PROTEIN KINASES; ENZYME ACTIVATION; GLYCINE; KINETICS; MAGNESIUM; MODELS, MOLECULAR; SERINE; THERMODYNAMICS; THREONINE;

EID: 73249119188     PISSN: 00062960     EISSN: None     Source Type: Journal    
DOI: 10.1021/bi901475g     Document Type: Article

References (98)

1. Smith, C. M., Radzio-Andzelm, E., Madhusudan, Akamine, P., and Taylor, S. S. (1999) The catalytic subunit of cAMP-dependent protein kinase: prototype for an extended network of communication. Prog. Biophys. Mol. Biol. 71, 313-341.
2. Taylor, S. S., Radzio-Andzelm, E., Madhusudan, Cheng, X., Ten Eyck, L., and Narayana, N. (1999) Catalytic subunit of cyclic AMP-dependent protein kinase: structure and dynamics of the active site cleft. Pharmacol. Ther. 82, 133-141.
3. Johnson, D. A., Akamine, P., Radzio-Andzelm, E., Madhusudan, and Taylor, S. S. (2001) Dynamics of cAMP-dependent protein kinase. Chem. Rev. 101, 2243-2270.
4. Nolen, B., Taylor, S., and Ghosh, G. (2004) Regulation of protein kinases: Controlling activity through activation segment conformation. Mol. Cell 15, 661-675.
5. Taylor, S. S., Kim, C., Vigil, D., Haste, N. M., Yang, J., Wu, J., and Anand, G. S. (2005) Dynamics of signaling by PKA. Biochim. Biophys. Acta 1754, 25-37.
6. Manning, G., Whyte, D. B., Martinez, R., Hunter, T., and Sudarsanam, S. (2002) The protein kinase complement of the human genome. Science 298, 1912-1934.
7. Adams, J. A. (2001) Kinetic and catalytic mechanisms of protein kinases. Chem. Rev. 101, 2271-2290.
8. Herberg, F. W., and Taylor, S. S. (1993) Physiological inhibitors of the catalytic subunit of cAMP-dependent protein kinase: effect of MgATP on protein-protein interactions. Biochemistry 32, 14015-14022.
9. Zimmermann, B., Schweinsberg, S., Drewianka, S., and Herberg, F. W. (2008) Effect of metal ions on high-affinity binding of pseudo-substrate inhibitors to PKA. Biochem. J. 413, 93-101.
10. Herberg, F. W., Yonemoto, W., and Taylor, S. S. (1993) The catalytic subunit of cAMP-dependent protein kinase. NATO ASI Ser., Ser. H 76, 203-213.
11. Taylor, S. S., Knighton, D. R., Zheng, J., Ten Fyck, L. F., and Sowadski, J. M. (1992) Structural framework for the protein kinase family. Annu. Rev. Cell Biol. 8, 429-462.
12. Taylor, S. S., Knighton, D. R., Zheng, J., Ten Eyck, L. F., and Sowadski, J. M. (1992) cAMP-dependent protein kinase and the protein kinase family. Faraday Discuss. 143-152.
13. Zheng, J., Knighton, D. R., Nguyen, H. X., Taylor, S. S., Sowadski, J. M., and Ten Eyck, L. F. (1993) Crystal structures of the myristylated catalytic subunit of cAMP-dependent protein kinase reveal open and closed conformations. Protein Sci. 2, 1559-1573.
14. Narayana, N., Cox, S., Nguyen-huu, X., Ten Eyck, L. F., and Taylor, S. S. (1997) A binary complex of the catalytic subunit of cAMP-dependent protein kinase and adenosine further defines conformational flexibility. Structure 5, 921-935.
15. Tsigelny, I., Greenberg, J. P., Cox, S., Nichols, W. L., Taylor, S. S., and Ten Eyck, L. F. (1999) 600 ps molecular dynamics reveals stable substructures and flexible hinge points in cAMP dependent protein kinase. Biopolymers 50, 513-524.
16. Helms, V., and McCammon, J. A. (1997) Kinase conformations: a computational study of the effect of ligand binding. Protein Sci. 6, 2336-2343.
17. Cheng, X., Shaltiel, S., and Taylor, S. S. (1998) Mapping substrate-induced conformational changes in cAMP-dependent protein kinase by protein footprinting. Biochemistry 37, 14005-14013.
18. Watson, J. D., and Milner-White, E. J. (2002) A novel main-chain anion-binding site in proteins: the nest. A particular combination of [phi],[psi] values in successive residues gives rise to anion-binding sites that occur commonly and are found often at functionally important regions. J. Mol. Biol. 315, 171-182.
19. Watson, J. D., and Milner-White, E. J. (2002) The conformations of polypeptide chains where the main-chain parts of successive residues are enantiomeric. Their occurrence in cation and anion-binding regions of proteins. J. Mol. Biol. 315, 183-191.
20. Madhusudan, Trafny, E. A., Nguyen Huu, X., Adams, J. A., Ten Eyck, L. F., Taylor, S. S., and Sowadski, J. M. (1994) cAMP-dependent protein kinase: crystallographic insights into substrate recognition and phosphotransfer. Protein Sci. 3, 176-187.
21. Karlsson, R., Madhusudan, Taylor, S. S., and Sowadski, J. M. (1994) Intermolecular contacts in various crystal forms related to the open and closed conformational states of the catalytic subunit of cAMP-dependent protein kinase. Acta Crystallogr., Sect D: Biol. Crystallogr. D50, 657-662.
22. Akamine, P., Madhusudan, Wu, J., Xuong, N.-H., Ten Eyck, L. F., and Taylor, S. S. (2003) Dynamic features of cAMP-dependent protein kinase revealed by apoenzyme crystal structure. J. Mol. Biol. 327, 159-171.
23. Herberg, F. W., Doyle, M. L., Cox, S., and Taylor, S. S. (1999) Dissection of the nucleotide and metal-phosphate binding sites in cAMP-dependent protein kinase. Biochemistry 38, 6352-6360.
24. Zheng, J., Knighton, D. R., Ten Eyck, L. F., Karlsson, R., Xuong, N. H., Taylor, S. S., and Sowadski, J. M. (1993) Crystal structure of the catalytic subunit of cAMP-dependent protein kinase complexed with MgATP and peptide inhibitor. Biochemistry 32, 2154-2161.
25. Yang, J., Ten Eyck, L. F., Xuong, N.-H., and Taylor, S. S. (2004) Crystal structure of a cAMP-dependent protein kinase mutant at 1.26 Å: New insights into the catalytic mechanism. J. Mol. Biol. 336, 473-487.
26. Shaltiel, S., Cox, S., and Taylor, S. S. (1998) Conserved water molecules contribute to the extensive network of interactions at the active site of protein kinase A. Proc. Natl. Acad. Sci. U.S.A. 95, 484-491.
27. Valiev, M., Kawai, R., Adams, J. A., and Weare, J. H. (2003) The role of the putative catalytic base in the phosphoryl transfer reaction in a protein kinase: First-principles calculations. J. Am. Chem. Soc. 125, 9926-9927.
28. Valiev, M., Yang, J., Adams, J. A., Taylor, S. S., and Weare, J. H. (2007) Phosphorylation reaction in cAPK protein kinase-free energy quantum mechanical/molecular mechanics simulations. J. Phys. Chem. B 111, 13455-13464.
29. Diaz, N., and Field, M. J. (2004) Insights into the phosphoryl-transfer mechanism of cAMP-dependent protein kinase from quantum chemical calculations and molecular dynamics simulations. J. Am. Chem. Soc. 126, 529-542.
30. Henkelman, G., LaBute, M. X., Tung, C.-S., Fenimore, P. W., and McMahon, B. H. (2005) Conformational dependence of a protein kinase phosphate transfer reaction. Proc. Natl. Acad. Sci. U.S.A. 102, 15347-15351.
31. Cheng, Y., Zhang, Y., and McCammon, J. A. (2005) How does the cAMP-dependent protein kinase catalyze the phosphorylation reaction: An ab initio QM/MM study. J. Am. Chem. Soc. 127, 1553-1562.
32. Cook, P. F., Neville, M. E. Jr., Vrana, K. E., Hartl, T. F., and Roskoski, R. Jr. (1982) Adenosine cyclic 30,50-monophosphate dependent protein kinase: Kinetic mechanism for the bovine skeletal muscle catalytic subunit. Biochemistry 21, 5794-5799.
33. Shaffer, J., and Adams, J. A. (1999) An ATP-linked structural change in protein kinase A precedes phosphoryl transfer under physiological magnesium concentrations. Biochemistry 38, 5572-5581.
34. Armstrong, R. N., Kondo, H., Granot, J., Kaiser, E. T., and Mildvan, A. S. (1979) Magnetic resonance and kinetic studies of the manganese-(II) ion and substrate complexes of the catalytic subunit of adenosine 3′,5′- monophosphate dependent protein kinase from bovine heart. Biochemistry 18, 1230-1238.
35. Granot, J., Mildvan, A. S., and Kaiser, E. T. (1980) Studies of the mechanism of action and regulation of cAMP-dependent protein kinase. Arch. Biochem. Biophys. 205, 1-17.
36. Adams, J. A., and Taylor, S. S. (1993) Divalent metal ions influence catalysis and active-site accessibility in the cAMP-dependent protein kinase. Protein Sci. 2, 2177-2186.
37. Shaffer, J., and Adams, J. A. (1999) Detection of conformational changes along the kinetic pathway of protein kinase A using a catalytic trapping technique. Biochemistry 38, 12072-12079.
38. Kornev, A. P., Haste, N. M., Taylor, S. S., and Eyck, L. F. (2006) Surface comparison of active and inactive protein kinases identifies a conserved activation mechanism. Proc. Natl. Acad. Sci. U.S.A. 103, 17783-17788.
39. Kannan, N., and Neuwald, A. F. (2005) Did protein kinase regulatory mechanism evolve through elaboration of a simple structural component? J. Mol. Biol. 351, 956-972.
40. Shan, Y., Seeliger, M. A., Eastwood, M. P., Frank, F., Xu, H., Jensen, M. O., Dror, R. O., Kuriyan, J., and Shaw, D. E. (2009) A conserved protonation-dependent switch controls drug binding in the Abl kinase. Proc. Natl. Acad. Sci. U.S.A. 106, 139-144.
41. Adams, J. A., and Taylor, S. S. (1992) Energetic limits of phosphotransfer in the catalytic subunits of cAMP-dependent protein kinase as measured by viscosity experiments. Biochemistry 31, 8516-8522.
42. Ni, D. Q., Shaffer, J., and Adams, J. A. (2000) Insights into nucleotide binding in protein kinase A using fluorescent adenosine derivatives. Protein Sci. 9, 1818-1827.
43. Neitzel, J. J., Dostmann, W. R. G., and Taylor, S. S. (1991) Role of magnesium-ATP in the activation and reassociation of cAMP-dependent protein kinase I: consequences of replacing the essential arginine in cAMP-binding site A. Biochemistry 30, 733-739.
44. Lew, J., Taylor, S. S., and Adams, J. A. (1997) Identification of a partially rate-determining step in the catalytic mechanism of cAMP-dependent protein kinase: A transient kinetic study using stopped-flow fluorescence spectroscopy. Biochemistry 36, 6717-6724.
45. Zhou, J., and Adams, J. A. (1997) Participation of ADP dissociation in the rate-determining step in cAMP-dependent protein kinase. Biochemistry 36, 15733-15738.
46. Bhatnagar, D., Roskoski, R., Rosendahl, M. S., and Leonard, N. J. (1983) Adenosine cyclic 30,50-monophosphate dependent protein kinase: a new fluorescence displacement titration technique for characterizing the nucleotide binding site on the catalytic subunit. Biochemistry 22, 6310-6317.
47. Qamar, R., Yoon, M.-Y., and Cook, P. F. (1992) Kinetic mechanism of the adenosine 3′,5′-monophosphate dependent protein kinase catalytic subunit in the direction of magnesium adenosine 5′-diphosphate phosphorylation. Biochemistry 31, 9986-9992.
48. Isralewitz, B., Baudry, J., Gullingsrud, J., Kosztin, D., and Schulten, K. (2001) Steered molecular dynamics investigations of protein function. J. Mol. Graphics Modell. 19, 13-25.
49. Leech, J., Prins, J. F., and Hermans, J. (1996) SMD: visual steering of molecular dynamics for protein design. IEEE Comput. Sci. Eng. 3, 38-45.
50. Grubmueller, H., Heymann, B., and Tavan, P. (1996) Ligand binding: molecular mechanics calculation of the streptavidin-biotin rupture force. Science 271, 997-999.
51. Lu, B., Wong, C. F., and McCammon, J. A. (2005) Release of ADP from the catalytic subunit of protein kinase A: A molecular dynamics simulation study. Protein Sci. 14, 159-168.
52. Klahn, M., Rosta, E., and Warshel, A. (2006) On the mechanism of hydrolysis of phosphate monoesters dianions in solutions and proteins. J. Am. Chem. Soc. 128, 15310-15323.
53. Warshel, A., Sharma, P. K., Kato, M., Xiang, Y., Liu, H., and Olsson, M. H. M. (2006) Electrostatic basis for enzyme catalysis. Chem. Rev. 106, 3210-3235.
54. - ions and their ion-pair through zwitterionic dimyristoyl phosphatidylcholine lipid bilayer by umbrella integration with harmonic fourier beads. J. Am. Chem. Soc. 131, 1706-1716.
55. Khavrutskii, I. V., Fajer, M., and McCammon, J. A. (2008) Intrinsic free energy of the conformational transition of the KcsA signature peptide from conducting to nonconducting state. J. Chem. Theor. Comp. 4, 1541-1554.
56. Khavrutskii, I. V., Dzubiella, J., and McCammon, J. A. (2008) Computing accurate potentials of mean force in electrolyte solutions with the generalized gradient-augmented harmonic Fourier beads method. J. Chem. Phys. 128 (044106), 1-13.
57. Khavrutskii, I. V., and McCammon, J. A. (2007) Generalized gradient-augmented harmonic Fourier beads method with multiple atomic and/or center-of-mass positional restraints. J. Chem. Phys. 127 (124901), 1-12.
58. Khavrutskii, I. V., Arora, K., and Brooks, C. L. III (2006) Harmonic fourier beads method for studying rare events on rugged energy surfaces. J. Chem. Phys. 125 (174108), 1-7.
59. Grant, B. J., Rodrigues, A. P., ElSawy, K. M., McCammon, J. A., and Caves, L. S. (2006) Bio3d: an R package for the comparative analysis of protein structures. Bioinformatics 22, 2695-2696.
60. Kornev, A. P., Taylor, S. S., and Ten Eyck, L. F. (2008) A helix scaffold for the assembly of active protein kinases. Proc. Natl. Acad. Sci. U.S.A. 105, 14377-14382.
61. MacKerell, A. D., Jr., Brooks, B. R., Brooks, C. L., III, Nilsson, L., Roux, B., Won, Y., Karplus, M. (1998) CHARMM: The energy function and its parameterization with an overview of the program, in The Encyclopedia of Computational Chemistry (Schleyer, P. v. R., Schreiner, P. R., Allinger, N. L., Clark, T., Gasteiger, J., Kollman, P., Henry F. Schaefer, I., Eds.) John Wiley & Sons, Chichester.
62. Phillips, J. C., Braun, R., Wang, W., Gumbart, J., Tajkhorshid, E., Villa, E., Chipot, C., Skeel, R. D., Kale, L., and Schulten, K. (2005) Scalable molecular dynamics with NAMD. J. Comput. Chem. 26, 1781-1802.
63. MacKerell, A. D. Jr.; et al. (1998) All-atom empirical potential for molecular modeling and dynamics Studies of proteins. J. Phys. Chem. B 102, 3586-3616.
64. MacKerell, A. D. Jr., Wiorkiewicz-Kuczera, J., and Karplus, M. (1995) An all-atom empirical energy function for the simulation of nucleic acids. J. Am. Chem. Soc. 117, 11946-11975.
65. Glenn, J. M., Douglas, J. T., and Michael, L. K. (1994) Constant pressure molecular dynamics algorithms. J. Chem. Phys. 101, 4177-4189.
66. Scott, E. F., Yuhong, Z., Richard, W. P., and Bernard, R. B. (1995) Constant pressure molecular dynamics simulation: The Langevin piston method. J. Chem. Phys. 103, 4613-4621.
67. Essmann, U., Perera, L., Berkowitz, M. L., Darden, T., Lee, H., and Pedersen, L. G. (1995) A smooth particle mesh Ewald method. J. Chem. Phys. 103, 8577-8593.
68. Darden, T., York, D., and Pedersen, L. G. (1993) Particle mesh Ewald: An N*log(N) method for Ewald sums in large systems. J. Chem. Phys. 98, 10089-10092.
69. Grubmueller, H., Heller, H., Windemuth, A., and Schulten, K. (1991) Generalized Verlet algorithm for efficient molecular dynamics simulations with long-range interactions. Mol. Simulation 6, 121-142.
70. Streett, W. B., Tildesley, D. J., and Saville, G. (1978) Multiple time-step methods in molecular dynamics. Mol. Phys. 35, 639-648.
71. Ryckaert, J.-P., Ciccotti, G., and Berendsen, H. J. C. (1977) Numerical integration of the cartesian equations of motion of a system with constraints: Molecular dynamics of n-alkanes. J. Comp. Phys. 23, 327-341.
72. Tobias, D. J., and Brooks, C. L. III (1988) Molecular dynamics with internal coordinate constraints. J. Chem. Phys. 89, 5115-5127.
73. Lazaridis, T., Tobias, D. J., Brooks, C. L. III, and Paulaitis, M. E. (1991) Reaction paths and free energy profiles for conformational transitions: an internal coordinate approach. J. Chem. Phys. 95, 7612-7625.
74. Roux, B., Nina, M., Pomes, R., and Smith, J. C. (1996) Thermodynamic stability of water molecules in the bacteriorhodopsin proton channel: A molecular dynamics free energy perturbation study. Biophys. J. 71, 670-681.
75. Gilson, M. K., Given, J. A., Bush, B. L., and McCammon, J. A. (1997) The statistical-thermodynamic basis for computation of binding affinities: A critical review. Biophys. J. 72, 1047-1069.
76. Hermans, J., and Wang, L. (1997) Inclusion of loss of translational and rotational freedom in theoretical estimates of free energies of binding. Application to a complex of benzene and mutant T4 lysozyme. J. Am. Chem. Soc. 119, 2707-2714.
77. Boresch, S., Tettinger, F., Leitgeb, M., and Karplus, M. (2003) Absolute binding free energies: A quantitative approach for their calculation. J. Phys. Chem. A 107, 9535-9551.
78. Deng, Y., and Roux, B. (2006) Calculation of standard binding free energies: Aromatic molecules in the T4 Lysozyme L99A Mutant. J. Chem. Theor. Comp. 2, 1255-1273.
79. Doudou, S., Burton, N. A., and Henchman, R. H. (2009) Standard free energy of binding from a one-dimensional potential of mean force. J. Chem. Theor. Comp. 5, 909-918.
80. Zhou, H.-X., and Gilson, M. K. (2009) Theory of free energy and entropy in noncovalent binding. Chem. Rev. 109, 4092-4107.
81. Knighton, D. R., Zheng, J. H., Ten Eyck, L. F., Xuong, N. H., Taylor, S. S., and Sowadski, J. M. (1991) Structure of a peptide inhibitor bound to the catalytic subunit of cyclic adenosine monophosphate-dependent protein kinase. Science 253, 414-420.
82. Gherman, B. F., Baik, M.-H., Lippard, S. J., and Friesner, R. A. (2004) Dioxygen activation in methane monooxygenase: A theoretical study. J. Am. Chem. Soc. 126, 2978-2990.
83. Torrent, M., Musaev, D. G., and Morokuma, K. (2001) The flexibility of carboxylate ligands in methane monooxygenase and ribonucleotide reductase: A density functional study. J. Phys. Chem. B 105, 322-327.
84. LeCloux, D. D., Barrios, A. M., Mizoguchi, T. J., and Lippard, S. J. (1998) Modeling the diiron centers of non-heme iron enzymes. Preparation of sterically hindered diiron(II) tetracarboxylate complexes and their reactions with dioxygen. J. Am. Chem. Soc. 120, 9001-9014.
85. Rardin, R. L., Tolman, W. B., and Lippard, S. J. (1991) Monodentate carboxylate complexes and the carboxylate shift: implications for polymetalloprotein structure and function. New J. Chem. 15, 417-430.
86. Sousa, S. F., Fernandes, P. A., and Ramos, M. J. (2007) The carboxylate shift in zinc enzymes: A computational study. J. Am. Chem. Soc. 129, 1378-1385.
87. Miyashita, O., Onuchic, J. N., and Wolynes, P. G. (2003) Nonlinear elasticity, proteinquakes, and the energy landscapes of functional transitions in proteins. Proc. Natl. Acad. Sci. U.S.A. 100, 12570-12575.
88. Sanders, C. R., Tian, G., and Tsai, M. D. (1989) Mechanism of adenylate kinase. Is there a relationship between local substrate dynamics, and local binding energy, and the catalytic mechanism? Biochemistry 28, 9028-9043.
89. Biondi, R. M., Komander, D., Thomas, C. C., Lizcano, J. M., Deak, M., Alessi, D. R., and van Aalten, D. M. F. (2002) High resolution crystal structure of the human PDK1 catalytic domain defines the regulatory phosphopeptide docking site. EMBO J. 21, 4219-4228.
90. Corbin, J. D., Keely, S. L., and Park, C. R. (1975) The distribution and dissociation of cyclic adenosine 3′:5′-monophosphate-dependent protein kinases in adipose, cardiac, and other tissues. J. Biol. Chem. 250, 218-225.
91. Whitehouse, S., and Walsh, D. A. (1983) Mg X ATP2-dependent interaction of the inhibitor protein of the cAMP-dependent protein kinase with the catalytic subunit. J. Biol. Chem. 258, 3682-3692.
92. Van Patten, S. M., Fletcher, W. H., and Walsh, D. A. (1986) The inhibitor protein of the cAMP-dependent protein kinase-catalytic subunit interaction. Parameters of complex formation. J. Biol. Chem. 261, 5514-5523.
93. Masterson, L. R., Mascioni, A., Traaseth, N. J., Taylor, S. S., and Veglia, G. (2008) Allosteric cooperativity in protein kinase A. Proc. Natl. Acad. Sci. U.S.A. 105, 506-511.
94. Zhou, J., and Adams, J. A. (1997) Is there a catalytic base in the active site of cAMP-dependent protein kinase? Biochemistry 36, 2977-2984.
95. Grant, B. D., and Adams, J. A. (1996) Pre-steady-state kinetic analysis of cAMP-dependent protein kinase using rapid quench flow techniques. Biochemistry 35, 2022-2029.
96. Huang, S. L., and Tsai, M. D. (1982) Does the magnesium(II) ion interact with the alpha-phosphate of ATP? An investigation by oxygen-17 nuclear magnetic resonance. Biochemistry 21, 951-959.
97. Yang, J., Kennedy, E. J., Wu, J., Deal, M. S., Pennypacker, J., Ghosh, G., and Taylor, S. S. (2009) Contribution of non-catalytic core residues to activity and regulation in protein kinase A. J. Biol. Chem. 284, 6241-6248.
98. Grant, B. D., Hemmer, W., Tsigelny, I., Adams, J. A., and Taylor, S. S. (1998) Kinetic analyses of mutations in the glycine-rich loop of cAMP-dependent protein kinase. Biochemistry 37, 7708-7715.