Applied and Environmental Microbiology, May 2001, p. 2183-2190, Vol. 67, No. 5
0099-2240/01/$04.00+0 DOI: 10.1128/AEM.67.5.2183-2190.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Instituto de Biotecnologia (INBIOTEC), Parque Cientifico de León, 24006 León,1 and Facultad de Ciencias Biológicas y Ambientales, Area de Microbiologia, Universidad de León, 24071 León,2 Spain
Received 5 December 2000/Accepted 22 February 2001
A cluster of six genes, tRNATrp-secE-nusG-rplK-rplA-pkwR, was cloned and sequenced from a Corynebacterium glutamicum cosmid library and shown to be contiguous in the C. glutamicum genome. These genes encode a tryptophanyl tRNA, the protein translocase component SecE, the antiterminator protein NusG, and the ribosomal proteins L11 and L1 in addition to PkwR, a putative regulatory protein of the LacI-GalR family. S1 nuclease mapping analysis revealed that nusG and rplK are expressed as separate transcriptional units and rplK and rplA are cotranscribed as a single mRNA. A 19-nucleotide inverted repeat that appears to correspond to a transcriptional terminator was located in the 3' region downstream from nusG. Northern analysis with different probes confirmed the S1 mapping results and showed that the secE-rplA four-gene region gives rise to four transcripts. secE was transcribed as a 0.5-kb monocistronic mRNA, nusG formed two transcripts of 1.4 and 1.0 kb from different initiation sites, and the two ribosomal protein genes rplK and rplA were cotranscribed as a single mRNA of 1.6 kb. A consensus L1 protein binding sequence was identified in the leader region of the rplK-rplA transcript, suggesting that expression of the rplK-rplA cluster was regulated by autogenous regulation exerted by the L1 protein at the translation level. The promoters of the nusG and rplK-rplA genes were subcloned in a novel corynebacterial promoter-probe vector and shown to confer strong expression of the reporter gene.
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