Hirofumi Yoshikawa

Isolation and characterization of the secE homologue gene of Bacillus subtilis

A 4.0 kb EcoRI fragment of Bacillus subtilis conferring thiostrepton resistance was cloned and characterized. By nucleotide sequencing of the relevant region, six open reading frames were established, which corresponded to a part of spoOH, a ribosomal protein gene (rpmG), an unidentified open reading frame (orfE), a transcription antiterminator gene nusG, and ribosomal protein genes rplK and rplA. The orfE‐encoded 59‐amino‐acid polypeptide had a low, but significant, sequence similarity with the car‐boxy‐terminal region of the Escherichia coli SecE protein. A cold‐sensitive secE mutation of E. coli was complemented by the plasmid‐borne orfE sequence. Furthermore, the normal processing of a proOmpA protein was observed when the secE cold‐sensitive strain carried an orfE plasmid, indicating that orfE is the secE homologue of B. subtilis. The B. subtilis secE has only one transmembrane sequence compared to the three in E. coli.

The effect ofspo0 mutations on the expression ofspo0A- andspo0F-lacZ fusions

SummaryWe have constructedspo0A-lacZ andspo0F-lacZ fusions with a temperate phage vector and have investigated howspo0 gene products are involved in the expression of each of these genes. The expression ofspo0A-lacZ andspo0F-lacZ was stimulated at about the time of cessation of vegetative growth in Spo+ cells. This stimulation ofspo0A-lacZ was impaired by mutations in thespo0B, D, E, F orH genes but was not affected by mutations in thespo0J orK genes. Similar results were obtained with thespo0F-lacZ fusion. The effect of thespo0A mutation onspo0A-lacZ expression was characteristic: thespo0A-directed β-galactosidase activity found during vegetative growth was significantly enhanced in thespo0A mutant. This result suggests thatspo0A gene expression is autoregulated being repressed by its own gene product. Another remarkable observation was the effect of thesof-1 mutation, which is known to be aspo0A allele; it suppressed the sporulation deficiency ofspo0B, spo0D andspo0F mutants. Thespo0A-lacZ stimulation, which is impaired by any one of thesespo0 mutations, was restored by the additionalsof-1 mutation.

Genetic study of a new early gene, comC-α, of bacteriophage T4

Abstract We have previously shown that an abortive infection of bacteriophage T4 in host Escherichia coli K-12 mutants ( tab C) is overcome by a mutant having a mutation, com C-α, being mapped near gene 39. In this study, we performed a genetic analysis of a mutation of com C-α type ( com C803). Furthermore, an amber mutant, am B58 com C803, was isolated and the am B58 mutation was demonstrated to be a second-site mutation in the comC-α gene. By deletion mapping, the am B58 mutation was mapped in a region between the left ends of deletions of del (39–56)5 and of del (39–56)11. From these results, we concluded that the com C-α gene is a new early gene.

Crystal structure of a polycyano–polycadmate hostclathrate including a charge-transfer complex of methylviologen dicationand mesitylene as a guest

The crystal structure of a methylviologen dication (MV2+)–mesitylene clathrate, one of a newly synthesized polycyano–polycadmate host clathrates, including a charge-transfer complex of MV2+ and an aromatic molecule, has been revealed by X-ray diffraction.

Polycyano–polycadmate host clathrates including a methylviologen dication. Syntheses, crystal structures and photo-induced reduction of methylviologen dication

A series of polycyano–polycadmate host clathrates including a methylviologen dication (MV2+), which is a strong electron acceptor, and an organic molecule, such as alcohols, haloalkanes, ethers and small aromatics, and two complexes built of a polycyano–polycadmate and MV2+ have been synthesized. Single crystal X-ray diffraction experiments on ten clathrates and the two complexes revealed their 3-D network polycyano–polycadmate structures constructed with Cd2+ ions and CN− bridges. The network structures are classified into five structure types. Type I, II and III were found in the clathrates, and Type IV and V were found in the two complexes. Type I and II have cage-like cavities and each of the cavities includes one guest, MV2+ or an organic molecule. Type III has a channel-like cavity where MV2+ ions and organic molecules are included. Type IV and V have 3-D cavities, the shape of which is neither cage-like nor channel-like, for embracing MV2+. Although all compounds were colorless and the formation of a charge transfer complex between MV2+ and a neutral guest in the clathrates was not confirmed from the crystal structure data and diffuse reflectance spectra, some of them showed a color change from colorless to blue on UV irradiation, which arose from the reduction of MV2+ to a methylviologen radical cation MV+˙.