Rate-limiting domain and loop motions in arginine kinase

Omar Davulcu, Jack J. Skalicky, Michael S. Chapman

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

Arginine kinase catalyzes the reversible transfer of a phosphoryl group between ATP and arginine. It is the arthropod homologue of creatine kinase, buffering cellular ATP levels. Crystal structures of arginine kinase, in substrate-free and substrate-bound forms, have revealed large conformational changes associated with the catalytic cycle. Recent nuclear magnetic resonance identified movements of the N-terminal domain and a loop comprising residues I182-G209 with conformational exchange rates in the substrate-free enzyme similar to the turnover rate. Here, to understand whether these motions might be rate-limiting, we determined activation barriers for both the intrinsic dynamics and enzyme turnover using measurements over a temperature range of 15-30 °C. 15N transverse relaxation dispersion yields activation barriers of 46 ± 8 and 34 ± 12 kJ/mol for the N-terminal domain and I182-G209 loop, respectively. An activation barrier of 34 ± 13 kJ/mol was obtained for enzyme turnover from steady-state kinetics. The similarity between the activation barriers is indeed consistent with turnover being limited by backbone conformational dynamics and pinpoints the locations of potentially rate-limiting motions.

Original languageEnglish (US)
Pages (from-to)4011-4018
Number of pages8
JournalBiochemistry
Volume50
Issue number19
DOIs
StatePublished - May 17 2011

ASJC Scopus subject areas

  • Biochemistry

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