Cellulose-binding polypeptides from Cellulomonas fimi: endoglucanase D (CenD), a family A beta-1,4-glucanase.
Five cellulose-binding polypeptides were detected in Cellulomonas fimi culture supernatants. Two of them are CenA and CenB, endo-beta-1,4-glucanases which have been characterized previously; the other three were previously uncharacterized polypeptides with apparent molecular masses of 120, 95, and 75 kDa. The 75-kDa cellulose-binding protein was designated endoglucanase D (CenD). The cenD gene was cloned and sequenced. It encodes a polypeptide of 747 amino acids. Mature CenD is 708 amino acids long and has a predicted molecular mass of 74,982 Da. Analysis of the predicted amino acid sequence of CenD shows that the enzyme comprises four domains which are separated by short linker polypeptides: an N-terminal catalytic domain of 405 amino acids, two repeated sequences of 95 amino acids each, and a C-terminal domain of 105 amino acids which is > 50% identical to the sequences of cellulose-binding domains in Cex, CenA, and CenB from C. fimi. Amino acid sequence comparison placed the catalytic domain of CenD in family A, subtype 1, of beta-1,4-glycanases. The repeated sequences are more than 40% identical to the sequences of three repeats in CenB and are related to the repeats of fibronectin type III. CenD hydrolyzed the beta-1,4-glucosidic bond with retention of anomeric configuration. The activities of CenD towards various cellulosic substrates were quite different from those of CenA and CenB.
Meinke
A
A
Department of Microbiology, University of British Columbia, Vancouver, Canada.
Gilkes
N R
NR
Kilburn
D G
DG
Miller
R C
RC
Warren
R A
RA
D000595:Amino Acid Sequence; D001483:Base Sequence; D002480:Cellulase / Q000235:genetics* / Q000276:immunology; D002482:Cellulose / Q000378:metabolism*; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics; D005353:Fibronectins / Q000235:genetics / Q000276:immunology; D016987:Gram-Positive Rods / Q000235:genetics*; D006868:Hydrolysis; D008969:Molecular Sequence Data; D011994:Recombinant Proteins / Q000096:biosynthesis; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013237:Stereoisomerism
D005353:Fibronectins; D011994:Recombinant Proteins; D002482:Cellulose; D002480:Cellulase