1e2a
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(New page: 200px<br /><applet load="1e2a" size="450" color="white" frame="true" align="right" spinBox="true" caption="1e2a, resolution 2.3Å" /> '''ENZYME IIA FROM THE L...)
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Revision as of 11:37, 20 November 2007
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ENZYME IIA FROM THE LACTOSE SPECIFIC PTS FROM LACTOCOCCUS LACTIS
Overview
BACKGROUND: The bacterial phosphoenolpyruvate: sugar phosphotransferase, system (PTS) is responsible for the binding, transmembrane transport and, phosphorylation of numerous sugar substrates. The system is also involved, in the regulation of a variety of metabolic and transcriptional processes., The PTS consists of two non-specific energy coupling components, enzyme I, and a heat stable phosphocarrier protein (HPr), as well as several, sugar-specific multiprotein permeases known as enzymes II. In most cases, enzymes IIA and IIB are located in the cytoplasm, while enzyme IIC acts as, a membrane channel. Enzyme IIAlactose belongs to the, lactose/cellobiose-specific family of enzymes II, one of four functionally, and structurally distinct groups. The protein, which normally functions as, a trimer, is believed to separate into its subunits after phosphorylation., RESULTS: The crystal structure of the trimeric enzyme IIAlactose from, Lactococcus lactis has been determined at 2.3 A resolution. The subunits, of the enzyme, related to each other by the inherent threefold rotational, symmetry, possess interesting structural features such as coiled-coil-like, packing and a methionine cluster. The subunits each comprise three helices, (I, II and III) and pack against each other forming a nine-helix bundle., This helical bundle is stabilized by a centrally located metal ion and, also encloses a hydrophobic cavity. The three phosphorylation sites (His78, on each monomer) are located in helices III and their sidechains protrude, into a large groove between helices I and II of the neighbouring subunits., A model of the complex between phosphorylated HPr and enzyme IIAlactose, has been constructed. CONCLUSIONS: Enzyme IIAlactose is the first, representative of the family of lactose/cellobiose-specific enzymes IIA, for which a three-dimensional structure has been determined. Some of its, structural features, like the presence of two histidine residues at the, active site, seem to be common to all enzymes no overall structural, homology is observed to any PTS proteins or to any other proteins in the, Protein Data Bank. Enzyme IIAlactose shows surface complementarity to the, phosphorylated form of HPr and several energetically favourable, interactions between the two molecules can be predicted.
About this Structure
1E2A is a Single protein structure of sequence from Lactococcus lactis with MG as ligand. Active as Protein-N(pi)-phosphohistidine--sugar phosphotransferase, with EC number 2.7.1.69 Full crystallographic information is available from OCA.
Reference
The structure of enzyme IIAlactose from Lactococcus lactis reveals a new fold and points to possible interactions of a multicomponent system., Sliz P, Engelmann R, Hengstenberg W, Pai EF, Structure. 1997 Jun 15;5(6):775-88. PMID:9261069
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