J Biol Chem, Vol. 274, Issue 46, 32847-32854, November 12, 1999
Biotin Protein Ligase from Saccharomyces
cerevisiae
THE N-TERMINAL DOMAIN IS REQUIRED FOR COMPLETE ACTIVITY
Steven W.
Polyak,
Anne
Chapman-Smith,
Peter J.
Brautigan, and
John
C.
Wallace
From the Department of Biochemistry, University of Adelaide,
Adelaide, South Australia SA 5005, Australia
Catalytically active biotin protein ligase from
Saccharomyces cerevisiae (EC 6.3.4.15) was overexpressed in
Escherichia coli and purified to near homogeneity in three
steps. Kinetic analysis demonstrated that the substrates ATP, biotin,
and the biotin-accepting protein bind in an ordered manner in the
reaction mechanism. Treatment with any of three proteases of differing specificity in vitro revealed that the sequence between
residues 240 and 260 was extremely sensitive to proteolysis, suggesting that it forms an exposed linker between an N-terminal 27-kDa domain and
the C-terminal 50-kDa domain containing the active site. The protease
susceptibility of this linker region was considerably reduced in the
presence of ATP and biotin. A second protease-sensitive sequence,
located in the presumptive catalytic site, was protected against
digestion by the substrates. Expression of N-terminally truncated
variants of the yeast enzyme failed to complement E. coli
strains defective in biotin protein ligase activity. In
vitro assays performed with purified N-terminally truncated
enzyme revealed that removal of the N-terminal domain reduced BPL
activity by greater than 3500-fold. Our data indicate that both the
N-terminal domain and the C-terminal domain containing the active site
are necessary for complete catalytic function.
Copyright © 1999 by The American Society for Biochemistry and Molecular Biology, Inc.