CLONING, DNA-SEQUENCING, AND EXPRESSION OF THE GENE ENCODING CLOSTRIDIUM-THERMOCELLUM CELLULASE CELJ, THE LARGEST CATALYTIC COMPONENT OF THE CELLULOSOME
Mm. Ahsan et al., CLONING, DNA-SEQUENCING, AND EXPRESSION OF THE GENE ENCODING CLOSTRIDIUM-THERMOCELLUM CELLULASE CELJ, THE LARGEST CATALYTIC COMPONENT OF THE CELLULOSOME, Journal of bacteriology, 178(19), 1996, pp. 5732-5740
The Clostridium thermocellum F1 celJ gene, encoding endoglucanase J (C
elJ), consists of an open reading frame (ORF) of 4,803 nucleotides and
encodes a protein of 1,601 amino acids with a molecular weight of 178
,055. The ORF was confirmed as cell by comparison with the N-terminal
sequence of a truncated CelJ derivative. CelJ is a modular enzyme comp
osed of N-terminal signal peptide and six domains in the following ord
er: an S-layer homology domain, a domain of unknown function (UD-1), a
subfamily El endoglucanase domain, a family J endoglucanase domain, a
docking domain, and another domain of unknown function (UD-2). UD-1 h
as no significant similarity to UD-2. CelJ hydrolyzed carboxymethylcel
lulose and xylan, and xylanase activity was ascribed to the family J d
omain. Antiserum raised against the truncated CelJ crossreacted with p
roteins contained in the cellulosome of C. thermocellum F1. These resu
lts strongly suggest that CelJ is equivalent to S-2, which was identif
ied as the largest catalytic component in the cellulosome of C. thermo
cellum YS. A second but incomplete ORF encoding an enzyme classified i
n subfamily E2 endoglucanase, was located downstream of celJ.