3pbg: Difference between revisions

The initial structural model of 6-phospho-beta-galactosidase from, Lactococcus lactis was refined to an R-factor of 16.4% (R[free] = 23.6%), to 2.3 A resolution (1 A = 0.1 nm), and the structures of three other, crystal forms were solved by molecular replacement. The four structural, models are essentially identical. The catalytic center of the enzyme is, approximately at the mass center of the molecule and can only be reached, through a 20 A long channel, which is observed with an "open" or "closed", entrance. The closed entrance is probably too small for the educt, lactose-6-phosphate to enter, but large enough for the first product, glucose to leave. Among the presented structures is a complex between an, almost inactive mutant and the second product galactose-6-phosphate, which, is exclusively bound at side-chains. A superposition (onto the native, enzyme) of galactose-6-phosphate as bound to the mutant suggests the, geometry of a postulated covalent intermediate. The binding mode of the, educt was modeled, starting from the bound galactose-6-phosphate. A, tightly fixed tryptophan is used as a chopping-board for splitting the, disaccharide, and several other aromatic residues in the active center, cavity are likely to participate in substrate transport/binding.

3PBG is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Lactococcus_lactis Lactococcus lactis] with SO4 as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/6-phospho-beta-galactosidase 6-phospho-beta-galactosidase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.2.1.85 3.2.1.85] Structure known Active Sites: ACA, ACB, PHA and PHB. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=3PBG OCA].  

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