PubMed · 4611329
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M Levinthal. 1974. Bacterial genetics excluding E. coli.. https://doi.org/10.1146/annurev.mi.28.100174.001251
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The gene cbhB from the cellulolytic bacterium Cellulomonas fimi encodes a polypeptide of 1090 amino acids. Cellobiohydrolase B (CbhB) is 1037 amino acids long, with a calculated molecular mass of 109765 Da. The enzyme comprises five domains: an N-terminal catalytic domain of 643 amino acids, three fibronectin type III repeats of 97 amino acids each, and a C-terminal cellulose-binding domain of 104 amino acids. The catalytic domain belongs to family 48 of glycosyl hydrolases. CbhB has a very low activity on CM-cellulose. Viscometric analysis of CM-cellulose hydrolysis indicates that the enzyme is an exoglucanase. Cellobiose is the major product of hydrolysis of cellulose. In common with two other exoglycanases from C. fimi, CbhB has low but detectable endoglucanase activity. CbhB is the second exo-cellobiohydrolase found in C. fimi. Therefore, the cellulase system of C. fimi resembles those of fungi in comprising multiple endoglucanases and cellobiohydrolases.
On the basis of NMR studies and analysis of the products of acid and alkaline hydrolyses the following structures were established for the repeating units of poly(arabitol phosphate) teichoic acid: alpha-6-deoxy-L-Talp-(1-->3)-beta-D-GLcpNAc-(1-->2)-alpha-L-Rha p-(1-->4(2)-D- Arabitol-PO4 and beta-D-GlcpNAc-(1-->2)-alpha-L-Rhap-(1-->4(2)-D-arabitol-PO4. The molar ratio of these units is about 1.2:1.0, respectively. Poly(arabitol phosphate) teichoic acid is here reported in bacterial cells walls for the first time.
The actinomycete Frankia alni fixes N2 in root nodules of several non-leguminous plants. It is one of the few known N2-fixing members of the high-GC Gram+ lineage of prokaryotes. Thus, we have undertaken a study of its nitrogen fixation gene (nif) organization to compare with that of the more extensively characterized proteobacteria. A cosmid (pFN1) containing the nif region of Fa CpI1 was isolated from a cosmid library using the nifHDK genes of Fa CpI1 as a probe. A 4.5-kb BamHI fragment that mapped downstream from the previously characterized nifHDK genes was cloned and sequenced. Based on nt and aa sequence similarities to nif from other N2-fixing bacteria, eight ORF were identified and designated nifX, orf3, orf1, nifW, nifZ, nifB, orf2 and nifU. A region that hybridized to Rhizobium meliloti and Klebsiella pneumoniae nifA did not appear to contain a nifA-like gene. We have revised the map of the Fa nif region to reflect current information.