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Catalytic dry run

Moving parts during catalysis (blue) and in the free enzyme (red) are overlapping. KERN/MACMILLAN

Enzymes are constantly rehearsing, say Elan Eisenmesser, Dorothee Kern (Brandeis University, Waltham, MA), and colleagues. They find that, even before a substrate appears on the scene, an enzyme flexes rapidly through its catalytic motions.

Kern has been looking at enzymes for many years, but in Eastern Europe her work was constrained. "We didn't have big enough NMR machines to look at the protein, so we were looking at the substrate during catalysis," she says. But now money and NMR technologies have caught up with Kern's ambitions. With new NMR methods, different protein conformations can be quantitated, thus yielding the kinetics of protein motion.

The Brandeis group applied these methods to the prolyl cis-trans isomerase cyclophilin A (CypA). They first mapped movements during catalysis, and then found that very similar movements happened with the free enzyme, with frequencies reflecting the turnover number of the enzyme. "All the motions are already there, and constantly going on, even with no substrate around," says Kern. "Nature has selected proteins so they are sampling defined conformations. They are optimized for catalysis."A single rate constant for these movements was consistent with the existence of an extensive, connected network of moving residues. Chemical shift changes caused by a collection of individual mutations could be cross-correlated, again suggesting the concerted movement of a network of residues.

Reference:

Eisenmesser, E.Z., et al. 2005. Nature. doi:10.1038/nature04105.

William A. Wells

wellsw{at}rockefeller.edu

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This Article Full Text (PDF, 633K) PPT slides of all figures Alert me when this article is cited Services Email this article Similar articles in this journal Alert me to new content in the JCB Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Wells, W. A. Search for Related Content PubMed Articles by Wells, W. A. Social Bookmarking                            What's this?