1ee3

From Proteopedia

proteopedia linkproteopedia link

spinqualitylabelsall models 1ee3, resolution 1.70Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

Cadmium-substituted bovine pancreatic carboxypeptidase A (alfa-form) at pH 7.5 and 2 mM chloride in monoclinic crystal form

Overview

Three high-resolution crystal structures of Cd(II)-substituted, carboxypeptidase A (CPA) have been determined by X-ray diffraction from, crystals prepared in three different buffer systems to assess the effect, of pH and ionic strength on the Cd(II) coordination geometry. All, crystallize in the space group P2(1) with identical cell dimensions., Cd-CPA(7.5): Cd(II)-substituted CPA prepared at pH 7.5 with [Cl(-)]=2 mM, determined to 1.70 A resolution ( R=17.4% and R(free)=19.8%); Cd-CPA(5.5):, Cd(II)-substituted CPA prepared at pH 5.5 with [Cl(-)]=2 mM to 2.00 A, resolution ( R=16.1% and R(free)=18.6%); Cd-CPA(7.5)-Cl:, Cd(II)-substituted CPA prepared at pH 7.5 with [Cl(-)]=250 mM to 1.76 A, resolution ( R=16.7% and R(free)=17.8%). No noticeable structural changes, were observed between the three structures. Two water molecules coordinate, to Cd(II), in contrast to the single water molecule coordinating to Zn(II), in the Zn-CPA structure. No binding sites for anions could be identified, even in the structure with a high concentration of chloride ions. It is, suggested that the anion inhibition is due to weak outer-sphere, association of Cl(-) ions at several binding sites, shielding the strong, positive charge distribution at the surface of the protein near the active, site. Based on structural data and a sequence alignment of 18, non-redundant carboxypeptidases, a more elaborate version of the earlier, reaction model is proposed that also addresses the transport of water to, and from the active site. Conserved residues whose function was not, addressed previously delineate the proposed pathways used in the transport, of water during catalysis.

About this Structure

1EE3 is a Single protein structure of sequence from Bos taurus with CD as ligand. Active as Carboxypeptidase A, with EC number 3.4.17.1 Full crystallographic information is available from OCA.

Reference

Three high-resolution crystal structures of cadmium-substituted carboxypeptidase A provide insight into the enzymatic function., Jensen F, Bukrinsky T, Bjerrum J, Larsen S, J Biol Inorg Chem. 2002 Apr;7(4-5):490-9. Epub 2002 Feb 15. PMID:11941507

Page seeded by OCA on Tue Nov 20 13:56:16 2007