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Journal of Bacteriology, December 1998, p. 6581-6585, Vol. 180, No. 24
Department of Chemical Engineering,
University of Rochester Rochester, New York 14627-0166
Received 8 July 1998/Accepted 8 October 1998
Clostridium thermocellum produces an extracellular
cellulase complex termed the cellulosome. It consists of a scaffolding protein, CipA, containing nine cohesin domains and a cellulose-binding domain, and at least 14 different enzymatic subunits, each containing a
conserved duplicated sequence, or dockerin domain. The
cohesin-dockerin interaction is responsible for the assembly of the
catalytic subunits into the cellulosome structure. Each duplicated
sequence of the dockerin domain contains a region bearing homology to
the EF-hand calcium-binding motif. Two subdomains, each containing
a putative calcium-binding motif, were constructed from
the dockerin domain of CelS, a major cellulosomal catalytic
subunit. These subdomains, called DS1 and DS2, were cloned by PCR and
expressed in Escherichia coli. The binding of DS1 and DS2
to R3, the third cohesin domain of CipA, was analyzed by nondenaturing
gel electrophoresis. A stable complex was formed only when R3 was
combined with both DS1 and DS2, indicating that the two halves of the
dockerin domain interact with each other and such interaction is
required for effective binding of the dockerin domain to the cohesin domain.
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Involvement of Both Dockerin Subdomains in Assembly
of the Clostridium thermocellum Cellulosome
*
Corresponding author. Mailing address: University of
Rochester, Department of Chemical Engineering, 206 Gavett Hall,
Rochester, NY 14627-0166. Phone: (716) 275-8499. Fax: (716) 442-6686. E-mail: davidwu{at}che.rochester.edu.
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