Cloning, sequencing and analysis of the ggh-A gene encoding a 1,4-beta-D-glucan glucohydrolase from Microbispora bispora.
The ggh-A gene, encoding a 1,4-beta-D-glucan glucohydrolase/beta-glucosidase, of Microbispora bispora (Mb) was subcloned and expressed from a 4.0-kb XhoI DNA fragment. The nucleotide sequence of this fragment was determined. Analysis of the sequence revealed one open reading frame (ORF) which encodes a 986-amino-acid (aa) protein with a calculated molecular weight of 107,510. The ggh-A ORF has features typical of an actinomycete gene including high GC content (70.5%) and corresponding biased codon usage. Comparison of the aa sequence of the Mb 1,4-beta-D-glucan glucohydrolase (Mbggh-A) with other glycosidases reveals high overall homology to several beta-glucosidases and a 1,4-beta-D-glucan glucohydrolase belonging to the glycosyl hydrolase family 3. The aa sequence alignments of Mbggh-A and beta-glucosidases show that the active site region potentially involves two Asp residues. The aa sequence homology studies revealed a potential two-domain structure for Mbggh-A and other beta-glucosidases. Furthermore, Mbggh-A has localized homology to a cellulose-binding domain present in some xylanases. This report is significant, as, to date, 1,4-beta-D-glucan glucohydrolases have rarely been reported, though they are assumed to have a critical role in cellulolysis.
Goyal
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Department of Biochemistry and Microbiology, Cook College, Rutgers, State University of New Jersey, New Brunswick 08903, USA. Goyal@mbcl.rutgers.edu
Eveleigh
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DE
D000192:Actinomycetales / Q000201:enzymology* / Q000235:genetics; D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites; D002482:Cellulose / Q000378:metabolism; D003001:Cloning, Molecular; D004274:DNA, Recombinant; D044643:Glucan 1,4-beta-Glucosidase; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D017386:Sequence Homology, Amino Acid; D001617:beta-Glucosidase / Q000235:genetics* / Q000378:metabolism
D004274:DNA, Recombinant; D002482:Cellulose; D001617:beta-Glucosidase; D044643:Glucan 1,4-beta-Glucosidase