Murein-lipoprotein of Escherichia coli: a protein involved in the stabilization of bacterial cell envelope

Two independent mutants of Escherichia coli lacking murein-lipoprotein have been found. One mutant whose mutation was named lpo was subjected to detailed analyses. The absence of both bound and unbound lipoproteins was shown by electrophoretic analysis of 14C-arginine labelled membrane proteins of the mutant. Nor was serologically cross-reacting material detected in the mutant by the Ouchterlony-method. Sequestering magnesium from mutant cell suspensions by ethylenediaminetetraacetic acid caused cell lysis, which was prevented in the presence of 0.5 M sucrose. Incubation in culture media at a very low level of magnesium resulted in the formation of blebs in the mutant. Examination of mutant cells by electron microscopy showed that the outer membrane of the mutant was uneven with small irregular protuberances, some of which pinched off forming vesicles of various sizes. Phosphotungstate used for negative-staining penetrated into the periplasmic space of the mutant cells. The mutants leaked a considerable fraction of their periplasmic enzymes. These physiological and morphological alterations in the lipoproteinless mutant suggest that murein-lipoprotein helps to maintain the outer envelope structure by connecting the outer membrane with murein so that the outer membrane may fulfil its physiological functions as a barrier to the environment.

Isolation of Q nucleoside precursor present in tRNA of an E. coli mutant and its characterization as 7-(cyano)-7-deazaguanosine

One of the E. coli mutants selected for deficiency of modified nucleoside Q was found to contain an analogue of Q and normal guanosine in place of Q. The analogue of Q, designated as preQo, was isolated on a large scale from purified tRNATyr containing preQo. The structure of preQo was determined to be 7-(cyano)-7-deazaguanosine by comparison of its ultraviolet absorption spectra, thin-layer chromatographic mobility and mass spectrum with those of synthetic material.

Crystallization of arginine-, formylmethionine-tyrosine-, and glycine-transfer RNAs from Escherichia coli

Crystals as large as 0.5 X 0.3 X 0.2 mm of purified arginine-transfer RNA from Escherichia coli have been prepared by a vapour diffusion method. X-ray diffraction photographs showed that the crystals gave reflections up to 3.7 A spacing. They have a trigonal space group P31 2 1 (OR P32 2 1) and cell-dimensions a=97.2, b=97.2, c=94.8A. Crystals of a mercury derivative of this transfer RNA have also been obtained, and an X-ray diffusion photography of one of them is presented. Formylmethionine-transfer RNA from E. coli was crystallized in various forms, and the appearance of the polymorphs was found to depend upon the amount of spermine in the solution from which the crystallization took place. Crystals of tyrosine-transfer RNA and glycine-transfer RNA have also been obtained.

Serum vitamin B12 levels of patients with rheumatoid arthritis

To elucidate the role of vitamin B12 in the formation of anemia in patients with rheumatoid arthritis serum B12 levels were investigated in patients with rheumatoid arthritis, patients with osteoarthritis and normal subject. Serum B12 level in patients with rheumatoid arthritis was significantly higher than that in patients with osteoarthritis and normal subjects. Serum B12 level increased in proportion to Steinbrocker's stages, and was related more closely to hemoglobin concentration than to erythrocyte count and had a high correlation with alpha1- and alpha2-globulin.

Isolation of a mutant of Escherichia coli lacking penicillin-sensitive D-alanine carboxypeptidase IA

A mutant of Escherichia coli that is deficient in D-alanine carboxypeptidase IA has been isolated. The enzyme is membrane bound and moderately sensitive to penicillin. It catalyzes in vitro both D-alanine carboxypeptidase and transpeptidase reactions. Being able to synthesize crosslinked peptidoglycan both in vivo and in vitro despite the absence of enzyme activity, the newly isolated mutant grew normally under a wide range of growth conditions. Therefore, this enzyme, like D-alanine carboxypeptidase IB, is not required for normal peptidoglycan synthesis in E. coli. The defect in the activity of D-alanine carboxypeptidase IA in the mutant however was not associated with disappearance of penicillin-binding proteins 5 and 6 (which have been shown to be D-alanine carboxypeptidase IA) or any of the other protein bands that bind [14C]penicillin G. Genetic mapping studies showed that the mutation (dacA) is located close to leuS(13.7 min) on the E. coli chromosome map. Double mutants (dacA dacB) that are deficient in both D-alanine carboxypeptidases IA and IB were obtained. These double mutants also were found to grow normally and to catalyze normal formation of crosslinked peptidoglycan.

[Angiographic demonstration of varices in the renal pelvis and the upper ureter (author's transl]

Two patients are described in whom varices in the renal pelves and upper ureters had been demonstrated angiographically. In the patients the varices were due to compression of the renal veins by the superior mesenteric artery. Renal vein varices should be considered as a cause of undiagnosed haematuria and, where necessary, phlebography should be carried out.

On the process of cellular division in Escherichia coli: a series of mutants of E. coli altered in the penicillin-binding proteins

A series of mutants defective in penicillin-binding components (or protein) (PBCs) was isolated from a collection of thermosensitive mutants of Escherichia coli. The mutants included mutations for each PBC (1 through 4) and a mutation in the activity of D-alanine carboxypeptidase 1a (PBC-5/6). PBC-1 was resolved into two components, PBC-1a and PBC-1b, which were the products of different genes referred to as ponA and ponB, respectively. No mutation examined in ponA-- or ponB--, by itself, was associated with a thermosensitive defect in growth. The mutants having ponB-- were hypersensitive to cephalosporins, which showed unusually high affinity to PBC-1a. Murein synthetic activity decreased markedly in cell-free preparations from the ponB-- mutant. The double mutation ponA-- ponB-- was found to be lethal. A mutant having ponAts and ponB-- revealed thermosensitivity of growth and lysed at the restrictive temperature. It is concluded that PBC-1a and PBC-1b could share a biochemical reaction necessary for cell elongation so that the function of either one may bypass the loss of the function of the other. With the series of mutants, the chromosomal locus of the gene for each PBC was mapped: ponA (PBC-1a) 73.5 min, ponB (PBC-1b) 3.3 min, rodA (PBC-2) 14.4 min, ftsI (PBC-3) 1.8 min, dacB (PBC-4) 68 min, and dacA (PBC-5/6) 13.7 min.

Amino acid replacement in a mutant lipoprotein of the Escherichia coli outer membrane

The primary structure of a mutant lipoprotein of the outer membrane of Escherichia coli was investigated. This mutant was previously described as a mutant that forms a dimer of the lipoprotein by an S-S bridge (H. Suzuki et al., J. Bacteriol. 127:1494-1501, 1976). The amino acid analysis of the mutant lipoprotein revealed that the mutant lipoprotein had an extra cysteine residue, with concomitant loss of an arginine residue. From the analysis of the mutant lipoprotein revealed that the mutant lipoprotein had an extra cysteine residue, with concomitant loss of an arginine residue. From the analysis of tryptic peptides, it was found that the arginine residue at position 57 was replaced with a cysteine residue. The amino terminal structure of the mutant lipoprotein was found to be glycerylcysteine, as in the case of the wild-type lipoprotein. The present results show that the mutation that was previously determined to map at 36.5 min on the E. coli chromosome occurred in the structure gene (lpp) for the lipoprotein. This was further confirmed by the fact that a merodiploid carrying both lpp+ and lpp produces not only the wild-type lipoprotein but also the mutant lipoprotein.

The use of two V-flaps for secondary correction of the cleft lip nose

Our new method for correction of the cleft lip nose with moderate deformity consists of shifting a V-shaped flap of alar cartilage and nostril lining medially at the tip of the nose, and shifting the alar base, as another V-flap, medially to the base of the columella. The latter creates a nostril sill.

Enzymatic solubilization of membrane immunoglobulin (M-Ig) from rabbit lymphocytes with phospholipase A2 (PL-A2) and phospholipase C (PL-C)

Enzymatic solubilization of M-Ig from rabbit lymph node cells was investigated using highly purified PL-A2 and PL-C. The combined treatment with PL-A2 (50 I.U./ml) and PL-C (20 I.U./ml) caused optimal solubilization of the membrane components from the 125I-labeled lymphocytes, but the treatment with either enzyme alone did not. The solubilized M-Ig was isolated and characterized as the membrane component which was specifically co-precipitable with homologous antigen-antibody complex. The solubilized M-Ig associated with some other membrane constituents was eluted in a void volume fraction by gelfiltration on a column of Sepharose 6B, and recovered at the interface between 30 and 40% sucrose layers by the density gradient centrifugation. The isolated component could be further separated by SDS-polyacrylamido gel electrophoresis into four radioactive polypeptides with apparent mol wt of 7 approximately 8 X 10(4), 4 approximately 5 X 10(4), 3 approximately 3.5 X 10(4) and 2 approximately 2.5 X 10(4), respectively. The results suggest that the enzymatic solubilization of lymphocyte M-Ig is a useful procedure to investigate further characteristics of M-Ig and their biological function related to the intracellular mechanisms of immune response.

Mutants of Escherichia coli lacking in highly penicillin-sensitive D-alanine carboxypeptidase activity

Mutants of Escherichia coli lacking in the highly penicillin-sensitive enzyme activities of D-carboxy-peptidase, transpeptidase, and endopeptidase, and with the concomitant absence of penicillin-binding protein 4 of B.G. Spratt and A.B. Pardee [(1975) Nature 254, 516-517] were isolated. The defect of these mutants is ascribed to the lack of an enzyme, D-alanine carboxypeptidase Ib. Genetic mapping studies show the mutation (dacB) to be located at 68 min on the E. coli chromosome map. The dacB mutation results in the simultaneous loss of D-alanine carboxypeptidase and penicillin-binding protein 4. The mutants grew normally under a wide range of growth conditions. We conclude that the enzyme is not a necessary component for normal peptidoglycan biosynthesis in E. coli.

On the process of cellular division in Escherichia coli: a mutant of E. coli lacking a murein-lipoprotein

A mutant of E. coli lacking a specific outer membrane lipoprotein was found. Both the free and the bound form have been lost in this mutant. No material that cross-reacted with antiserum against lipoprotein was detected by the Ouchterlony test. The mutant was defective in producing mRNA active for lipoprotein synthesis. The mutation leading to the loss of lipoprotein synthesis, referred to as lpo, seems to have arisen during production of an F'. The map position of lpo was at 36.5 min on the E. coli K12 map, in the order man, uidA, lpo, aroD, pps. The lpo mutant grew and divided normally and remained susceptible to bacteriophages lambda, phi80, P1, P2, the T series, and f1, f2, and MS2 in its male derivatives. The mutant was hypersensitive to EDTA and cationic dves and somewhat sensitive to detergents. There was considerable leakage of periplasmic enzymes but passive transport of beta-galactoside was unchanged. These physiological characteristics of the mutant suggest that lipoprotein is involved in maintaining the integrity of the outer envelope structure, by bridging the outer membrane and murein, but not in the vital processes of growth and division.