Assignment of the apolipoprotein A-I gene to 11q23 based on RFLP in a case with a partial deletion of chromosome 11, del(11)(q23.3→qter)

Summary The XmnI genotype at the apolipoprotein A-I locus was heterozygous in a boy with partial deletion of the long arm of chromosome 11, del(11)(q23.3qter). The apolipoprotein A-I gene, previously assigned to chromosome region 11q23q24, has been more specifically localized to 11q23 by excluding the region 11q24qter.     

Mutual interactions between optic lobe circadian pacemakers in the cricket Gryllus bimaculatus

The coupling mechanism between the bilaterally paired optic lobe circadian pacemakers in the cricket Gryllus bimaculatus was investigated by recording locomotor activity, under constant light or constant red light, after the optic nerve was unilaterally severed.

Peptidoglycan synthetic activities in membranes of Escherichia coli caused by overproduction of penicillin-binding protein 2 and rodA protein

Penicillin-binding protein (PBP)-2 and the RodA protein are known to function in determining the rod shape of Escherichia coli cells. Peptidoglycan biosynthetic reactions that required these two proteins were demonstrated in the membrane fraction prepared from an E. coli strain that overproduced both of these two proteins and which lacked PBP-1B activity (the major peptidoglycan synthetase activity in the normal E. coli membranes). The cross-linked peptidoglycan was synthesized from UDP-N-acetylmuramylpentapeptide and UDP-N-acetylglucosamine in the presence of a high concentration of cefmetazole that inhibited all of PBPs except PBP-2. The peptidoglycan was synthesized via a lipid intermediate and showed up to 30% cross-linking. The cross-linking reaction was strongly inhibited by the amidinopenicillin, mecillinam, and by other beta-lactam antibiotics that have a high affinity for PBP-2, but not by beta-lactams that had very low affinity for PBP-2. The formation of peptidoglycan required the presence of high levels of both PBP-2 and the RodA protein in the membranes, but it is unclear which of the two proteins was primarily responsible for the extension of the glycan chains (transglycosylation). However, the sensitivity of the cross-linking reaction to specific beta-lactam antibiotics strongly suggested that it was catalyzed by PBP-2. The transglycosylase activity of the membranes was sensitive to enramycin and vancomycin and was unusual in being stimulated greatly by a high concentration of a chelating agent.     

A photosystem other than PS370 also mediates the negative phototaxis of Halobacterium halobium

Abstract It was found that a photorepellent system other than photosystem 370 (PS370) also controls the behavior of Halobacterium halobium . Both the dependence of background illumination and wavelength where the response showed maximum action distinguished that photosystem from PS370 whose photoreceptor pigment is thought to be an intermediate of s-rhodopsin (sR). A mutant strain that has no detectable activity in PS370 and in photoattractant response was isolated. This mutant strain showed the repellent response due to the new photosystem.     

Purification and characterization of the tween-hydrolyzing esterase of Mycobacterium smegmatis.

An esterase hydrolyzing Tween 80 (polyoxyethylene sorbitan monooleate) was purified from sonicated cell lysates of Mycobacterium smegmatis ATCC 14468 by DEAE-cellulose, Sephadex G-150, phenyl Sepharose, and diethyl-(2-hydroxypropyl) aminoethyl column chromatography and by subsequent preparative polyacrylamide gel electrophoresis. The molecular weight was estimated to be 36,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and 41,000 by gel filtration on a Sephadex G-150 column. The esterase contained a single polypeptide. The esterase was stable to heat treatment at 100 degrees C and to a wide range of pH. The temperature and pH optima for the hydrolysis of Tween 80 were 50 degrees C and 8.3, respectively. The esterase had a narrow substrate specificity; it exhibited a high activity only on compounds having both polyoxyethylene and fatty acyl moieties, such as Tweens. Monoacylglyceride was hydrolyzed more slowly by this esterase and this enzyme exhibited a nonspecific esterase activity on p-nitrophenyl acyl esters, especially those having short chain acyl moieties. The Km and Vmax were 19.2 mM and 1,670 mumol/min per mg of protein for Tween 20, 6.6 mM and 278 mumol/min per mg of protein for Tween 80, and 0.25 mM and 196 mumol/min per mg of protein for p-nitrophenyl acetate, respectively. Observations of the effects of various chemical modifications on the activity of the esterase indicated that tyrosine, histidine, arginine, and methionine (with tryptophan) residues may be active amino acids which play important roles in the expression of Tween 80-hydrolyzing activity of the enzyme.     

A possible role of protein kinase C in signal-induced lysosomal enzyme release

In platelets, activation of protein kinase C and mobilization of Ca2+ were selectively induced by the addition of 1-oleoyl-2-acetyl-glycerol and a low concentration of A23187, respectively (Kaibuchi, K., Takai, Y., Sawamura, M., Hoshijima, M., Fujikura, T. and Nishizuka, Y. (1983) J. Biol. Chem. 258, 6701-6704). Using this procedure evidence was obtained suggesting that the protein phosphorylation and Ca2+ mobilization were both essential and synergistically effective to cause release of lysosomal acid hydrolases such as N-acetylglucosaminidase. A similar observation was made for the lysosomal enzyme release from rat neutrophils.     

A novel complex mutation in the LDL receptor gene probably caused by the simultaneous occurrence of deletion and insertion in the same region

A novel complex mutation with the presence of both deletion and insertion in very close proximity in the same region was detected in exon 8 of the LDL receptor gene from two apparently unrelated Japanese families with familial hypercholesterolemia (FH). In this mutant LDL receptor gene, the nine bases from nucleotide (nt) 1115 to nt 1123 (AGGGTGGCT) were replaced by six different bases (CACTGA), and consequently the four amino acids from codon 351 to 354, Glu-Gly-Gly-Tyr, were replaced by three amino acids, Ala-Leu-Asn, in the conserved amino acid region of the growth factor repeat B of the LDL receptor. The nature of the amino acid substitution and data on the families suggest that this mutation is very likely to affect the LDL receptor function and cause FH. The generation of this complex mutation can be explained by the simultaneous occurrence of deletion and insertion through the formation of a hairpin-loop structure mediated by inverted repeat sequences. Thus this mutation supports the hypothesis that inverted repeat sequences influence the stability of a given gene and promote human gene mutations.     

Data on the CGG repeat at the fragile X site in the non-retarded Japanese population and family suggest the presence of a subgroup of normal alleles predisposing to mutate

The fragile X mutation is the result of amplification in the repeat number of p(CGG) _n in FMR-1; alleles with more than 52 repeats have been shown to be so unstable as to mutate in the repeat number in almost every transmission. To improve our understanding of mutations in normal alleles of FMR-1, the following studies were carried out in the Japanese population: a study on length variation in the repeat to determine the allele distribution of the repeat length in a non-retarded population, family studies to observe new mutations in normal allele, and haplotype analyses with microsatellite markers flanking the repeat to confirm estimated mutation rates and founder chromosomes in the fragile X syndrome. Analysis of the p(CGG) _n in 370 unrelated males detected 24 distinct alleles with repeats of 18–44. A comparison with previously reported data suggests the presence of racial/ethnic differences in the allele distribution. No premutation allele was found in 824 unrelated X chromosomes examined by the polymerase chain reaction and Southern blot analysis. Family studies detected one new mutation in a total of 303 meioses. However, the mutation rate was not in accordance with the expected or observed heterozygosities in the population or with linkage disequilibrium observed between the repeat numbers and the haplotypes of the markers flanking the CGG. The haplotype in the chromosome in which the new mutation was found was the same as that frequently found in the Japanese fragile X chromosomes, and the variance in the CGG repeat number was wider in chromosomes with the haplotypes frequently found in the fragile X chromosome than in those with the other haplotypes. These observations suggest that a subgroup is present in normal alleles and that this subgroup is more liable to mutate than others.