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L M Robson

Publications and source records attributed to L M Robson.

4 recordsLinked to original sources
PubMed1987

Endo-beta-1,4-glucanase gene of Bacillus subtilis DLG.

The DNA sequence of the Bacillus subtilis DLG endo-beta-1,4-glucanase gene was determined, and the in vivo site of transcription initiation was located. Immediately upstream from the transcription start site were sequences closely resembling those recognized by B. subtilis sigma 43-RNA polymerase. Two possible ribosome-binding sites were observed downstream from the transcription start site. These were followed by a long open reading frame capable of encoding a protein of ca. 55,000 daltons. A signal sequence, typical of those present in gram-positive organisms, was observed at the amino terminus of the open reading frame. Purification of the mature exocellular beta-1,4-glucanase and subsequent amino-terminal protein sequencing defined the site of signal sequence processing to be between two alanine residues following the hydrophobic portion of the signal sequence. The probability of additional carboxy-terminal processing of the beta-1,4-glucanase precursor is discussed. S1 nuclease protection studies showed that the amount of beta-1,4-glucanase mRNA in cells increased significantly as the culture entered the stationary phase. In addition, glucose was found to dramatically stimulate the amount of beta-1,4-glucanase mRNA in vivo. Finally, the specific activities of purified B. subtilis DLG endo-beta-1,4-glucanase and Trichoderma reesei QM9414 endo-beta-1,4-glucanase (EC 3.2.1.4) were compared by using the noncrystalline cellulosic substrate trinitrophenyl-carboxymethyl cellulose.

Amino Acid Sequence↗
PubMed1986

Cloning of the Bacillus subtilis DLG beta-1,4-glucanase gene and its expression in Escherichia coli and B. subtilis.

The gene encoding beta-1,4-glucanase in Bacillus subtilis DLG was cloned into both Escherichia coli C600SF8 and B. subtilis PSL1, which does not naturally produce beta-1,4-glucanase, with the shuttle vector pPL1202. This enzyme is capable of degrading both carboxymethyl cellulose and trinitrophenyl carboxymethyl cellulose, but not more crystalline cellulosic substrates (L. M. Robson and G. H. Chambliss, Appl. Environ. Microbiol. 47:1039-1046, 1984). The beta-1,4-glucanase gene was localized to a 2-kilobase (kb) EcoRI-HindIII fragment contained within a 3-kb EcoRI chromosomal DNA fragment of B. subtilis DLG. Recombinant plasmids pLG4000, pLG4001a, pLG4001b, and pLG4002, carrying this 2-kb DNA fragment, were stably maintained in both hosts, and the beta-1,4-glucanase gene was expressed in both. The 3-kb EcoRI fragment apparently contained the beta-1,4-glucanase gene promoter, since transformed strains of B. subtilis PSL1 produced the enzyme in the same temporal fashion as the natural host B. subtilis DLG. B. subtilis DLG produced a 35,200-dalton exocellular beta-1,4-glucanase; intracellular beta-1,4-glucanase was undetectable. E. coli C600SF8 transformants carrying any of the four recombinant plasmids produced two active forms of beta-1,4-glucanase, an intracellular form (51,000 +/- 900 daltons) and a cell-associated form (39,000 +/- 400 daltons). Free exocellular enzyme was negligible. In contrast, B. subtilis PSL1 transformed with recombinant plasmid pLG4001b produced three distinct sizes of active exocellular beta-1,4-glucanase: approximately 36,000, approximately 35,200, and approximately 33,500 daltons. Additionally, B. subtilis PSL1(pLG4001b) transformants contained a small amount (5% or less) of active intracellular beta-1,4-glucanase of three distinct sizes: approximately 50,500, approximately 38,500 and approximately 36,000 daltons. The largest form of beta-1,4-glucanase seen in both transformants may be the primary, unprocessed translation product of the gene.

Bacillus subtilis↗