1p52
From Proteopedia
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Structure of Arginine kinase E314D mutant
Overview
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.
About this Structure
1P52 is a Single protein structure of sequence from Limulus polyphemus with NO3, MG, ADP and DAR as ligands. Active as Arginine kinase, with EC number 2.7.3.3 Full crystallographic information is available from OCA.
Reference
The putative catalytic bases have, at most, an accessory role in the mechanism of arginine kinase., Pruett PS, Azzi A, Clark SA, Yousef MS, Gattis JL, Somasundaram T, Ellington WR, Chapman MS, J Biol Chem. 2003 Jul 18;278(29):26952-7. Epub 2003 May 5. PMID:12732621
Page seeded by OCA on Tue Nov 20 23:28:52 2007
