2air
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(New page: 200px<br /><applet load="2air" size="450" color="white" frame="true" align="right" spinBox="true" caption="2air, resolution 2.0Å" /> '''T-state Active Site o...)
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Revision as of 06:01, 21 November 2007
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T-state Active Site of Aspartate Transcarbamylase:Crystal Structure of the Carbamyl Phosphate and L-alanosine Ligated Enzyme
Overview
An X-ray diffraction study to 2.0 A resolution shows that this enzyme, ATCase, is in the T-state (the c3 to c3 distance is 45.2 A) when ATCase is, bound to carbamyl phosphate (CP) and to L-alanosine (an analogue of, aspartate). This result strongly supports the kinetic results that, alanosine did not inhibit the carbamylation of aspartate in the normal, reaction of native ATCase plus CP and aspartate [Baillon, J., Tauc, P., and Herve, G. (1985) Biochemistry 24, 7182-7187]. The structure further, reveals that the phosphate of CP is 4 A away from its known position in, the R-state and is in the T-state position of P(i) in a recent study of, ATCase complexed with products, phosphate (P(i)) and, N-carbamyl-L-aspartate [Huang, J., and Lipscomb, W. N. (2004) Biochemistry, 43, 6422-6426]. Moreover, the alanosine position in this T-state is, somewhat displaced from that expected for its analogue, aspartate, from, the R-state position. The relations of these structural aspects to the, kinetics are presented.
About this Structure
2AIR is a Protein complex structure of sequences from Escherichia coli with ZN, CP and AL0 as ligands. Active as Aspartate carbamoyltransferase, with EC number 2.1.3.2 Full crystallographic information is available from OCA.
Reference
T-state active site of aspartate transcarbamylase: crystal structure of the carbamyl phosphate and L-alanosine ligated enzyme., Huang J, Lipscomb WN, Biochemistry. 2006 Jan 17;45(2):346-52. PMID:16401065
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