2qxt
|
Crystal Structure Analysis of the Bacillus subtilis lipase crystallized at pH 4.5
OverviewOverview
Understanding the structural basis of altered properties of proteins due, to changes in temperature or pH provides useful insights in designing, proteins with improved stability. Here we report the basis for the, pH-dependent thermostability of the Bacillus subtilis lipase (Lip A) using, spectroscopic and X-ray crystallographic studies. At pH values above 7, lipase denatures and aggregates when heated at temperatures above 45, degrees C. However, at pH below 6 lipase denatures upon heating but the, activity and its native structure of lipase is completely recovered upon, cooling. In order to obtain the structural basis of this unusual stability, of lipase, we determined high-resolution crystal structures of the lipase, in two different crystal forms at pH 4.5 and 5. These structures show, linear oligomerization of lipase using only two types of dimeric, associations and these inter-molecular interactions are completely absent, in several crystal forms of wild-type and mutant proteins obtained at, basic pH. In accordance with the crystallographic studies, spectroscopic, investigations reveal an invariant secondary structure in the pH range of, 4-10. Quaternary organization of lipase at low pH resulted in changes in, the tryptophan environment and binding of 1-anilino-8-naphthalene sulfate, (ANS) at low pH. Low pH stability of the lipase is not observed in the, presence of sodium chloride (>0.2 M) indicating the importance of ionic, interactions at low pH. Inter- and intra-molecular ionic interactions that, occur at pH below 6.0 are proposed to trap the molecule in a conformation, that allows its complete refolding upon cooling.
About this StructureAbout this Structure
2QXT is a Single protein structure of sequence from Bacillus subtilis. Active as Triacylglycerol lipase, with EC number 3.1.1.3 Full crystallographic information is available from OCA.
ReferenceReference
Structural basis for the remarkable stability of Bacillus subtilis lipase (Lip A) at low pH., Rajakumara E, Acharya P, Ahmad S, Sankaranaryanan R, Rao NM, Biochim Biophys Acta. 2007 Nov 12;. PMID:18053819
Page seeded by OCA on Wed Feb 13 08:18:32 2008