2c0r: Difference between revisions
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==Overview== | ==Overview== | ||
pH is one of the key parameters that affect the stability and function of, proteins. We have studied the effect of pH on the, pyridoxal-5'-phosphate-dependent enzyme phosphoserine aminotransferase, produced by the facultative alkaliphile Bacillus circulans ssp., alkalophilus using thermodynamic and crystallographic analysis. Enzymatic, activity assay showed that the enzyme has maximum activity at pH 9.0 and, relative activity less than 10% at pH 7.0. Differential scanning, calorimetry and circular dichroism experiments revealed variations in the, stability and denaturation profiles of the enzyme at different pHs. Most, importantly, release of pyridoxal-5'-phosphate and protein thermal, denaturation were found to occur simultaneously at pH 6.0 in contrast to, pH 8.5 where denaturation ... | pH is one of the key parameters that affect the stability and function of, proteins. We have studied the effect of pH on the, pyridoxal-5'-phosphate-dependent enzyme phosphoserine aminotransferase, produced by the facultative alkaliphile Bacillus circulans ssp., alkalophilus using thermodynamic and crystallographic analysis. Enzymatic, activity assay showed that the enzyme has maximum activity at pH 9.0 and, relative activity less than 10% at pH 7.0. Differential scanning, calorimetry and circular dichroism experiments revealed variations in the, stability and denaturation profiles of the enzyme at different pHs. Most, importantly, release of pyridoxal-5'-phosphate and protein thermal, denaturation were found to occur simultaneously at pH 6.0 in contrast to, pH 8.5 where denaturation preceded cofactor's release by approximately 3, degrees C. To correlate the observed differences in thermal denaturation, with structural features, the crystal structure of phosphoserine, aminotransferase was determined at 1.2 and 1.5 A resolution at two, different pHs (8.5 and 4.6, respectively). Analysis of the two structures, revealed changes in the vicinity of the active site and in surface, residues. A conformational change in a loop involved in substrate binding, at the entrance of the active site has been identified upon pH change., Moreover, the number of intramolecular ion pairs was found reduced in the, pH 4.6 structure. Taken together, the presented kinetics, thermal, denaturation, and crystallographic data demonstrate a potential role of, the active site in unfolding and suggest that subtle but structurally, significant conformational rearrangements are involved in the stability, and integrity of phosphoserine aminotransferase in response to pH changes. | ||
==About this Structure== | ==About this Structure== | ||
2C0R is a | 2C0R is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Bacillus_circulans Bacillus circulans] with PLP as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/Phosphoserine_transaminase Phosphoserine transaminase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.6.1.52 2.6.1.52] Structure known Active Site: AC1. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=2C0R OCA]. | ||
==Reference== | ==Reference== | ||
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[[Category: transferase]] | [[Category: transferase]] | ||
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