Termination of a transcription unit comprising highly expressed genes in the archaebacterium Methanococcus voltae.

The 3'termini of transcripts originating from genes organized in a highly expressed transcription unit were analyzed in the archaebacterium Methanococcus voltae. The putative termination signals were found in an AT-rich intergenic region following the 3'-terminal gene. The two detected signals both contain oligo(T) sequences. A possible stem/loop structure immediately precedes one of the oligo(T) tracts. This secondary structure is considered to have an additional function in stabilizing the transcripts

Conserved elements in the transcription initiation regions preceding highly expressed structural genes of methanogenic archaebacteria.

The sequences of the intergenic regions of the strongly expressed genes encoding methyl CoM reductase in three different methanogenic archaebacteria were determined and the 5'-ends of the transcripts were mapped. After alignment, consensus sequences were found which are located both upstream and downstream of the transcription starts. They correspond, in part, to those previously characterized as putative elements of archaebacterial promoter sequences. In addition, bending of the DNA in front of the transcription start sites was shown in two cases and a characteristic common DNA structure immediately downstream of the 5'-end of the transcript was discovered. This structure was also found in the corresponding regions of previously described genes in methanogens. Our results suggest that both sequence and structural information may have roles in the initiation of transcription of protein encoding genes of these archaebacteria

Identification and sequence analysis of the Bacillus subtilis W23 xylR gene and xyl operator.

The xyl operator of Bacillus subtilis W23 was identified by deletion analysis of the xyl regulatory region as a 25-base-pair (bp) sequence located 10 bp downstream from the xyl promoter. The outer 10 bp of the xyl operator exhibit perfect palindromic symmetry, while 5 central bp are nonpalindromic. It was demonstrated that the penultimate base pair near the end of this sequence is important for repressor binding. The location of the xylR gene encoding the repressor was determined by its ability to mediate xylose-dependent repression of a xyl-cat fusion on a multicopy plasmid. The nucleotide sequence of 1,355 bp from this DNA was analyzed and contains an open reading frame with a coding capacity for 384 amino acids leading to a protein with a calculated molecular weight of 42,270. A mutant with a deletion in this reading frame showed no repression of the xyl-cat fusion. The coding sequence is preceded by a suitable ribosome-binding sequence and uses GTG as a start codon and TAA as a stop codon. The relationship of these results to corresponding data obtained from B. subtilis 168 is discussed

Cloning and characterization of the methyl coenzyme M reductase genes from Methanobacterium thermoautotrophicum.

The genes coding for methyl coenzyme M reductase were cloned from a genomic library of Methanobacterium thermoautotrophicum Marburg into Escherichia coli by using plasmid expression vectors. When introduced into E. coli, the reductase genes were expressed, yielding polypeptides identical in size to the three known subunits of the isolated enzyme, alpha, beta, and gamma. The polypeptides also reacted with the antibodies raised against the respective enzyme subunits. In M. thermoautotrophicum, the subunits are encoded by a gene cluster whose transcript boundaries were mapped. Sequence analysis revealed two more open reading frames of unknown function located between two of the methyl coenzyme M reductase genes

A conjugation-like mechanism for prespore chromosome partitioning during sporulation in Bacillus subtilis

Spore formation in Bacillus subtilis begins with an asymmetric cell division that superficially resembles the division of vegetative cells. Mutations in the spoIIIE gene of B. subtilis partially block partitioning of one chromosome into the smaller (prespore) compartment of the sporulating cell. Point mutations that specifically block prespore chromosome partitioning affect a carboxy-terminal domain of SpoIIIE that shows significant sequence similarity to the DNA transfer (Tra) proteins of several conjugative plasmids of Streptomyces. In wild-type sporulating cells, the prespore chromosome passes through an intermediate stage resembling the state in which spoIIIE mutant cells are blocked. The prespore chromosome is then transferred progressively through the newly formed spore septum. We propose that translocation of the prespore chromosome occurs by a mechanism that is functionally related to the conjugative transfer of plasmid DNA