X-ray crystallographic characterization of the Co(II)-substituted Tris-bound form of the aminopeptidase from Aeromonas proteolytica |
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Authors: | Munih Petra Moulin Aaron Stamper Carin C Bennett Brian Ringe Dagmar Petsko Gregory A Holz Richard C |
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Institution: | Program in Biophysics and Structural Biology, Rosenstiel Basic Medical Sciences Research Center, Brandeis University, 415 South Street, Waltham, MA 02254, United States. |
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Abstract: | The X-ray crystal structure of the Co(II)-loaded form of the aminopeptidase from Aeromonas proteolytica (CoCo(AAP)]) was solved to 2.2A resolution. CoCo(AAP)] folds into an alpha/beta globular domain with a twisted beta-sheet hydrophobic core sandwiched between alpha-helices, identical to ZnZn(AAP)]. Co(II) binding to AAP does not introduce any major conformational changes to the overall protein structure and the amino acid residues ligated to the dicobalt(II) cluster in CoCo(AAP)] are the same as those in the native Zn(II)-loaded structure with only minor perturbations in bond lengths. The Co(II)-Co(II) distance is 3.3A. Tris(hydroxymethyl)aminomethane (Tris) coordinates to the dinuclear Co(II) active site of AAP with one of the Tris hydroxyl oxygen atoms (O4) forming a single oxygen atom bridge between the two Co(II) ions. This is the only Tris atom coordinated to the metals with Co1-O and Co2-O bonds distances of 2.2 and 1.9A, respectively. Each of the Co(II) ions resides in a distorted trigonal bipyramidal geometry. This important structure bridges the gap between previous structural and spectroscopic studies performed on AAP and is discussed in this context. |
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Keywords: | Hydrolysis Aminopeptidase Zinc Cobalt EPR Electronic absorption X-ray crystallography Tris |
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