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Prorein Science (1997), 61375-1386. Cambridge University Press. Printed in the USA. Copyright 0 1997 The Protein Society
 

Summary: Prorein Science (1997), 61375-1386. Cambridge University Press. Printed in the USA.
Copyright 0 1997 The Protein Society
Conformational substates in enzyme mechanism:
The 120 K structure of a-lytic protease
at 1.5 A resolution
STEPHEN D. RADER' AND DAVID A. AGARD2
'Graduate Group in Biophysics
2HowardHughes Medical Institute and Department of Biochemistry and Biophysics,
University of California at San Francisco, San Francisco,California 94143-0448
(RECEIVEDNovember 25, 1996;ACCEPTEDMarch19, 1997)
Abstract
Insight into the dynamic properties of a-lytic protease (aLP) has been obtained through the use of low-temperature
X-ray crystallography and multiple-conformation refinement. Previous studies of aLP have shown that the residues
around the active site are ableto move significantly to accommodate substrates of different sizes. Here we show a link
between the ability to accommodate ligands and the dynamics of the binding pocket. Although the structure of aLP at
120 K hasE-factors with a uniformly low value of 4.8 A* for the main chain,four regions stand outas having
significantly higher E-factors. Because thermal motion should be suppressed at cryogenic temperatures, the high
E-factors are interpreted as the result of trapped conformational substates. The active site residues that are perturbed
during accommodation of different substrates are precisely those showing conformational substates, implying that
substrate binding selects a subset of conformations from the ensemble of accessible states. To better characterize the

  

Source: Agard, David - Department of Biochemistry and Biophysics, University of California at San Francisco
Rader, Stephen - Chemistry Program, University of Northern British Columbia

 

Collections: Biology and Medicine; Biotechnology; Chemistry