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PDBsum entry 3wt4
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References listed in PDB file
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Key reference
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Title
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Structural and kinetic bases for the metal preference of the m18 aminopeptidase from pseudomonas aeruginosa.
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Authors
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D.D.Nguyen,
R.Pandian,
D.Kim,
S.C.Ha,
H.J.Yoon,
K.S.Kim,
K.H.Yun,
J.H.Kim,
K.K.Kim.
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Ref.
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Biochem Biophys Res Commun, 2014,
447,
101-107.
[DOI no: ]
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PubMed id
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Abstract
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The peptidases in clan MH are known as cocatalytic zinc peptidases that have two
zinc ions in the active site, but their metal preference has not been rigorously
investigated. In this study, the molecular basis for metal preference is
provided from the structural and biochemical analyses. Kinetic studies of
Pseudomonas aeruginosa aspartyl aminopeptidase (PaAP) which belongs to peptidase
family M18 in clan MH revealed that its peptidase activity is dependent on
Co(2+) rather than Zn(2+): the kcat (s(-1)) values of PaAP were 0.006, 5.10 and
0.43 in no-metal, Co(2+), and Zn(2+)conditions, respectively. Consistently,
addition of low concentrations of Co(2+) to PaAP previously saturated with
Zn(2+) greatly enhanced the enzymatic activity, suggesting that Co(2+)may be the
physiologically relevant cocatalytic metal ion of PaAP. The crystal structures
of PaAP complexes with Co(2+) or Zn(2+) commonly showed two metal ions in the
active site coordinated with three conserved residues and a bicarbonate ion in a
tetragonal geometry. However, Co(2+)- and Zn(2+)-bound structures showed no
noticeable alterations relevant to differential effects of metal species, except
the relative orientation of Glu-265, a general base in the active site. The
characterization of mutant PaAP revealed that the first metal binding site is
primarily responsible for metal preference. Similar to PaAP, Streptococcus
pneumonia glutamyl aminopeptidase (SpGP), belonging to aminopeptidase family M42
in clan MH, also showed requirement for Co(2+) for maximum activity. These
results proposed that clan MH peptidases might be a cocatalytic cobalt peptidase
rather than a zinc-dependent peptidase.
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