1hn1
From Proteopedia
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E. COLI (LAC Z) BETA-GALACTOSIDASE (ORTHORHOMBIC)
Overview
Flash-freezing, which has become routine in macromolecular X-ray, crystallography, causes the crystal to contract substantially. In the case, of Escherichia coli beta-galactosidase the changes are reversible and are, shown to be due to lattice repacking. On cooling, the area of the protein, surface involved in lattice contacts increases by 50 %. There are, substantial alterations in intermolecular contacts, these changes being, dominated by the long, polar side-chains. For entropic reasons such, side-chains, as well as surface solvent molecules, tend to be somewhat, disordered at room temperature but can form extensive hydrogen-bonded, networks on cooling. Low-temperature density measurements suggest that, at, least in some cases, the beneficial effect of cryosolvents may be due to a, density increase on vitrification which reduces the volume of bulk solvent, that needs to be expelled from the crystal. Analysis of beta-galactosidase, and several other proteins suggests that both intramolecular and, intermolecular contact interfaces can be perturbed by cryocooling but that, the changes tend to be more dramatic in the latter case. The, temperature-dependence of the intermolecular interactions suggests that, caution may be necessary in interpreting protein-protein and, protein-nucleic acid interactions based on low-temperature crystal, structures.
About this Structure
1HN1 is a Single protein structure of sequence from Escherichia coli with MG and NA as ligands. Active as 4-hydroxybenzoyl-CoA thioesterase, with EC number 3.1.2.23 Full crystallographic information is available from OCA.
Reference
Reversible lattice repacking illustrates the temperature dependence of macromolecular interactions., Juers DH, Matthews BW, J Mol Biol. 2001 Aug 24;311(4):851-62. PMID:11518535
Page seeded by OCA on Tue Nov 20 16:39:54 2007
