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Journal of Bacteriology, May 1999, p. 2816-2822, Vol. 181, No. 9
Department of Microbiology,
Received 27 July 1998/Accepted 26 February 1999
A Clostridium histolyticum 116-kDa collagenase has an
H415EXXH motif but not the third zinc ligand, as found in
already characterized zinc metalloproteinases. To identify its
catalytic site, we mutated the codons corresponding to the three
conserved residues in the motif to other amino acid residues. The
mutation affecting His415 or His419 abolished
catalytic activity and zinc binding, while that affecting Glu416 did the former but not the latter. These results
suggest that the motif forms the catalytic site. We also mutated the
codons corresponding to other amino acid residues that are likely zinc ligands. The mutation affecting Glu447 decreased markedly
both the enzymatic activity and the zinc content, while that affecting
Glu446 or Glu451 had smaller effects on
activity and zinc binding. These mutations caused a decrease in
kcat but no significant change in
Km. These results are consistent with the
hypothesis that Glu447 is the third zinc ligand. The
spacing of the three zinc ligands is the same in all known clostridial
collagenases but not in other known gluzincins, indicating that they
form a new gluzincin subfamily. The effects of mutations affecting
Glu446 and Glu451 suggest that the two
residues are also involved in catalysis, possibly through an
interaction with the two zinc-binding histidine residues.
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Identification of Metal Ligands in the
Clostridium histolyticum ColH Collagenase
*
Corresponding author. Mailing address: Department of
Microbiology, Faculty of Medicine, Kagawa Medical University, 1750-1 Miki-cho, Kita-gun, Kagawa 761-0793, Japan. Phone: 81-87-898-5111. Fax:
81-87-891-2129. E-mail: microbio{at}kms.ac.jp.
Journal of Bacteriology, May 1999, p. 2816-2822, Vol. 181, No. 9
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
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