1P50

Transition state structure of an Arginine Kinase mutant

Summary for 1P50

• Entry DOI: 10.2210/pdb1p50/pdb
• Descriptor: Arginine kinase, MAGNESIUM ION, ADENOSINE-5'-DIPHOSPHATE, ... (6 entities in total)
• Functional Keywords: phosphagen kinase, transition state, transferase
• Biological source: Limulus polyphemus (Atlantic horseshoe crab)
• Cellular location: Cytoplasm: P51541
• Total number of polymer chains: 1
• Total formula weight: 40806.30

Authors

Pruett, P.S.,Azzi, A.,Clark, S.A.,Yousef, M.S.,Gattis, J.L.,Somasundarum, T.,Ellington, W.R.,Chapman, M.S. (deposition date: 2003-04-24, release date: 2003-06-17, Last modification date: 2023-08-16)

Primary citation

Pruett, P.S.,Azzi, A.,Clark, S.A.,Yousef, M.S.,Gattis, J.L.,Somasundaram, T.,Ellington, W.R.,Chapman, M.S.
The putative catalytic bases have, at most, an accessory role in the mechanism of arginine kinase.
J.Biol.Chem., 278:26952-26957, 2003

PubMed Abstract: Arginine kinase is a member of the phosphagen kinase family that includes creatine kinase and likely shares a common reaction mechanism in catalyzing the buffering of cellular ATP energy levels. Abstraction of a proton from the substrate guanidinium by a catalytic base has long been thought to be an early mechanistic step. The structure of arginine kinase as a transition state analog complex (Zhou, G., Somasundaram, T., Blanc, E., Parthasarathy, G., Ellington, W. R., and Chapman, M. S. (1998) Proc. Natl. Acad. Sci. U. S. A. 95, 8449-8454) showed that Glu-225 and Glu-314 were the only potential catalytic residues contacting the phosphorylated nitrogen. In the present study, these residues were changed to Asp, Gln, and Val or Ala in several single and multisite mutant enzymes. These mutations had little impact on the substrate binding constants. The effect upon activity varied with reductions in kcat between 3000-fold and less than 2-fold. The retention of significant activity in some mutants contrasts with published studies of homologues and suggests that acid-base catalysis by these residues may enhance the rate but is not absolutely essential. Crystal structures of mutant enzymes E314D at 1.9 A and E225Q at 2.8 A resolution showed that the precise alignment of substrates is subtly distorted. Thus, pre-ordering of substrates might be just as important as acid-base chemistry, electrostatics, or other potential effects in the modest impact of these residues upon catalysis.

PubMed: 12732621
DOI: 10.1074/jbc.M212931200

Experimental method

X-RAY DIFFRACTION (2.8 Å)