title: X-ray crystallographic characterization of the Co(II)-substituted Tris-bound form of the aminopeptidase from Aeromonas proteolytica.
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.
authors.affiliation: Program in Biophysics and Structural Biology, Rosenstiel Basic Medical Sciences Research Center, Brandeis University, 415 South Street, Waltham, MA 02254, United States.
authors.forename: Petra
authors.initials: P
authors.lastname: Munih
authors.forename: Aaron
authors.initials: A
authors.lastname: Moulin
authors.forename: Carin C
authors.initials: CC
authors.lastname: Stamper
authors.forename: Brian
authors.initials: B
authors.lastname: Bennett
authors.forename: Dagmar
authors.initials: D
authors.lastname: Ringe
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Petsko
authors.forename: Richard C
authors.initials: RC
authors.lastname: Holz
mesh_terms: D000333:Aeromonas / Q000201:enzymology*; D000626:Aminopeptidases / Q000737:chemistry* / Q000378:metabolism*; D001665:Binding Sites; D003035:Cobalt / Q000737:chemistry* / Q000378:metabolism; D003460:Crystallization; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D008666:Metalloendopeptidases / Q000737:chemistry / Q000378:metabolism; D017510:Protein Folding; D014325:Tromethamine; D015032:Zinc / Q000737:chemistry
chemical_list: D014325:Tromethamine; D003035:Cobalt; D000626:Aminopeptidases; D008666:Metalloendopeptidases; D015032:Zinc