Unusual sequence organization in CenB, an inverting endoglucanase from Cellulomonas fimi

J Bacteriol. 1991 Jan;173(1):308-14. doi: 10.1128/jb.173.1.308-314.1991.

Abstract

The nucleotide sequence of the cenB gene was determined and used to deduce the amino acid sequence of endoglucanase B (CenB) of Cellulomonas fimi. CenB comprises 1,012 amino acids and has a molecular weight of 105,905. The polypeptide is divided by so-called linker sequences rich in proline and hydroxyamino acids into five domains: a catalytic domain of 607 amino acids at the N terminus, followed by three repeats of 98 amino acids each which are greater than 60% identical, and a C-terminal domain of 101 amino acids which is 50% identical to the cellulose-binding domains of C. fimi cellulases Cex and CenA. A deletion mutant of the cenB gene encodes a polypeptide lacking the C-terminal 333 amino acids of CenB. The truncated polypeptide is catalytically active and, like intact CenB, binds to cellulose, suggesting that CenB has a second cellulose-binding site. The sequence of amino acids 1 to 461 of CenB is 35% identical, with a further 15% similarity, to that of a cellulase from avocado, which places CenB in cellulase family E. CenB releases mostly cellobiose and cellotetraose from cellohexaose. Like CenA, CenB hydrolyzes the beta-1,4-glucosidic bond with inversion of the anomeric configuration. The pH optimum for CenB is 8.5, and that for CenA is 7.5.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Base Sequence
  • Cellulase / genetics*
  • Cellulase / metabolism
  • Chromosome Deletion
  • Codon / genetics
  • Genes, Bacterial*
  • Gram-Positive Bacteria / enzymology
  • Gram-Positive Bacteria / genetics*
  • Kinetics
  • Molecular Sequence Data
  • Plants / enzymology
  • Plants / genetics
  • Sequence Homology, Nucleic Acid

Substances

  • Codon
  • Cellulase

Associated data

  • GENBANK/M55263
  • GENBANK/M55488
  • GENBANK/M55489
  • GENBANK/M55490
  • GENBANK/M55491
  • GENBANK/M55492
  • GENBANK/M55493
  • GENBANK/M55494
  • GENBANK/M64644
  • GENBANK/M93064