Primary structure of tRNA-Lys of E. coli B.

The primary structure of tRNALys of E. coli was determined by use of [32P]-tRNA. The sequence is pGGGUCGUUAGCUCAGDDGGDAGAGCAGUUGACUmam5-s2-UUU-t6AApsiCAAUUGm7GXCGCAGGTpsiCGAAUCCUGCACGACCCACCA. No s4-U was detected in position 8. No other lysine tRNA was detected but the existence of another species has not been ruled out.     

B22Asn人胰岛素突变体的研究

通过ＤＮＡ定点突变法将人胰岛素Ｂ２２Ａｒｇ改造成Ｂ２２Ａｓｎ,去除其一级结构中碱性蛋白酶位点,以期提高胰岛素在体内的稳定性。突变体基因克隆到表达载体ｐＢＶ２２０中,在Ｅ．ｃｏｌｉＤＨ５α中进行表达。分离纯化后的表达产物经胰蛋白酶和羧肽酶Ｂ联合作用获得重组Ｂ２２Ａｓｎ－人胰岛素．该突变胰岛素具有抗胰蛋白酶水解能力,但是其与受体的结合能力只有标准猪胰岛素的１２．４％．胰岛素结构中Ｂ２２Ａｒｇ可能在胰岛素与其受体结合过程中起重要作用。     

Nucleic acid synthesis in mustard gas-treated E. coli B

Following exposure to dilute aqueous solutions of mustard gas, suspensions of E. coli B do not produce DNA although PNA is formed in nearly normal amounts. When the treated cells are infected with virus T₂, DNA is synthesized and RNA is not. The DNA formation continued after the virus titer reached a maximum.     

解淀粉芽胞杆菌启动基因的克隆及其对地衣杆菌α-淀粉酶基因的调控

用大肠杆菌启动基因探针质粒pHE5克隆了解淀粉芽胞杆菌的启动基因。供体菌DNA的HindⅢ片段与pHE5重组后转化大肠杆菌,获得一批带启动基因的抗四环素转化子,其中四株的抗性达到200μg/mL,从这四株高抗性转化子中提取质粒,并对其中的一个重组质粒pAE23的插入片段进行限制性图谱分析和缺失研究,获得了一个缺失了部份片段,四环素抗性仍达到200μg/mL的衍生质粒pAED23,经酶切分析证明其上的启动基因位于0.8kb的EcoR Ⅰ—HindⅢ片段上。点杂交分析证实该片段来自解淀粉芽胞杆菌的DNA。将地衣杆菌的α-淀粉酶基因亚克隆至pAED23启动基因下游的HindⅢ位点上能增强该基因在大肠杆菌中的表达。     

Primary structure of tRNA Arg II of E. coli B.

tRNA Arg II of E. coli has 77 nucleotides. There are eight minor nucleotides including inosine and 2-methyladenosine. Except for a few differences, the structure of tRNA Arg II is very similar to the structure of tRNA Arg I reported by Murao et al.3. The major difference is in the size of dihydrouridine loop. tRNA Arg II does not contain 2-thiocytosine. The unidentified nucleoside X seems to be a different modification other than nucleoside N reported to be present in tRNA Arg I.     

Induction of pyrimidine nucleoside metabolizing enzymes in E. coli B

Induction studies on pyrimidine metabolizing enzymes in E. coli B have shown that the enzymes fall into three distinct groups according to their induction pattern. a) Cytidine deaminase and uridine phosphorylase, are induced by cytidine, CMP and adenosine; no induction was observed with uridine and AMP; b) thymidine phosphorylase is induced by cytidine, adenosine, all deoxyribonucleosides, CMP, deoxyribonucleotides, deoxyribose and deoxyribose-1-phosphate; c) uridine-cytidine kinase, uracil phosphoribosyltransferase, 5'-nucleotidase, thymidine kinase, are uninducible enzymes. Simultaneous addition of cytidine and glucose partially overcomes the cytidine deaminase and uridine phosphorylase induction. Cytidine deaminase reaches its maximum activity levels, in E. coli growing cells in presence of cytidine, two hours before the uridine phosphorylase activity. Maximum glucose repression of cytidine deaminase and uridine phosphorylase was obtained in correspondence of maximum cytidine induction.     

Zur Protoplastierung von E. coli B mit Lysozym und Versen

Zusammenfassung Die Einwirkung von Lysozym und Versen auf Zellen von E. coli B wird untersucht. Während die kombinierte Einwirkung, wie von Repaske (1956) beschrieben, zu Protoplasten führt, entstehen bei der alleinigen Einwirkung von Lysozym Halbprotoplasten. Diese unterscheiden sich äußerlich nicht von Bakterien, vermehren sich normal, platzen aber beim Verdünnen in dest. Wasser. Die Einwirkung von Versen allein hat keinen sichtbaren Erfolg, beeinträchtigt aber das Adsorptionsvermögen für den Phagen T 4. Beide Befunde werden in ihrem Zusammenhang mit der Wandstruktur der Zellen diskutiert.     

Recombinant plasmids capable to replication in B. subtilis and E. coli.

Summary The plasmid pBC16 (4.25 kbases), originally isolated from Bacillus cereus, determines tetracycline resistance and can be transformed into competent cells of B. subtilis. A miniplasmid of pBC16 (pBC16-1), 2,7 kb) which has lost an EcoRI fragment of pBC16 retains the replication functions and the tetracycline resistance. This plasmid which carries only one EcoRI site has been joined in vitro to pBS1, a cryptic plasmid previously isolated from B. subtilis and shown to carry also a single EcoRI site (Bernhard et al., 1978). The recombinant plasmid is unstable and dissociates into the plasmid pBS161 (8.2 kb) and the smaller plasmid pBS162 (2.1 kb). Plasmid pBS161 retains the tetracycline resistance. It possesses a single EcoRI site and 6 HindIII sites. The largest HindIII fragment of pBS161 carries the tetracycline resistance gene and the replication function. After circularization in vitro of this fragment a new plasmid, pBS161-1 is generated, which can be used as a HindIII and EcoRI cloning vector in Bacillus subtilis.Hybrid plasmids consisting of the E. coli plasmids pBR322, pWL7 or pAC184 and different HindIII fragments of pBS161 were constructed in vitro. Hybrids containing together with the E. coli plasmid the largest HindIII fragment of pBS161 can replicate in E. coli and B. subtilis. In E. coli only the replicon of the E. coli plasmid part is functioning whereas in B. subtilis replication of the hybrid plasmid is under the control of the Bacillus replicon. The tetracycline resistance of the B. subtilis plasmid is expressed in E. coli, but several antibiotic resistances of the E. coli plasmids (ampicillin, kanamycin and chloramphenicol) are not expressed in B. subtilis. The hybrid plasmids seem to be more unstable in B. subtilis than in E. coli.