Codon usage and G+C content in Bradyrhizobium japonicum genes are not uniform

To date, the sequences of 45 Bradyrhizobium japonicum genes are known. This provides sufficient information to determine their codon usage and G+C content. Surprisingly, B. japonicum nodulation and NifA-regulated genes were found to have a less biased codon usage and a lower G+C content than genes not belonging to these two groups. Thus, the coding regions of nodulation genes and NifA-regulated genes could hardly be identified in codon preference plots whereas this was not difficult with other genes. The codon frequency table of the highly biased genes was used in a codon preference plot to analyze the RSRj9 sequence which is an insertion sequence (IS)-like element. The plot helped identify a new open reading frame (ORF355) that escaped previous detection because of two sequencing errors. These were now corrected. The deduced gene product of ORF355 in RSRj9 showed extensive similarity to a putative protein encoded by an ORF in the T-DNA of Agrobacterium rhizogenes. The DNA sequences bordering both ORFs showed inverted repeats and potential target site duplications which supported the assumption that they were IS-like elements.     

Phage resistance and altered growth habit in a strain of Streptococcus bovis

Bacteriophage (phi Sb01) of Streptococcus bovis, isolated from pooled rumen fluid of cattle, was a small siphovirus of morphotype B1. It contained double-stranded DNA of length 30.9 kb, which was digested by the restriction endonucleases, EcoRI, HindIII, and PvuII. Bacteria which survived phi Sb01 infection (strain 2BAr) grew in long chains (100-200 cells), ultimately forming large clumps of cells. This growth habit was in distinct contrast to that of the parent host strain which grew predominantly in the form of single cells or diplococci. Strain 2BAr was genetically stable, resistant to phi Sb01 attack, and the observed differences in the growth characteristics of the parent strain and 2BAr indicated that cells of 2BAr were more adherent. In the rumen ecosystem, the selection of phage-resistant bacteria with altered growth characteristics may be a factor in modifying bacterial phenotypes, and thus increasing variability among bacteria which are closely related genetically.     

Dissociation of proteinase-inhibitor complexes by trichloroacetate

It was demonstrated that the addition of high concentrations of the chaotrope, sodium trichloroacetate, to proteinase assays provided for a dissociation of proteinase-inhibitor complexes. The complexes evaluated contained a heat-stable, polypeptide inhibitor of cysteine proteinases isolated from the cellular slime mold, Dictyostelium discoideum. The proteinases that were present in separate complexes included either D. discoideum proteinases or the plant proteinase papain. The general assay procedures described may be useful in detection of endogenous proteinase-inhibitor complexes in many systems.     

The benthic phase of the life cycle ofParapenaeus longirostris (Crustacea,Decapoda, Penaeidae) along the Mediterranean coast of Israel

The population ofP. longirostris along the Mediterranean coast of Israel spends the benthic phase of its life cycle (from body size over 15 mm) on muddy bottom deeper than 45 m. New age groups are recruited within the depth zone of 45–300 m and migrate in both inshore and offshore directions. Inshore migration is limited by unsuitable sandy ground. The limiting line for offshore migration was not found.An age group could be detected during one year within a body size range of TL = 40 mm to TL = 84.5 mm for males and to TL = 102.5 mm for females. Reproductive activity in shallow water, down to a depth of 73 m, takes place during the whole year, while in depths of 150–300 m there is an arrest of reproductive activity from June to August.     

A map of barley chromosome 2 using isozymic and morphological markers

The F₂ progeny of a cross between a chromosome 2 multiple marker stock and an adapted cultivar of barley were analyzed for four morphological markers and electrophoretic patterns of eight leaf isozymes. TheIdh-2 locus was linked to thePer-5 locus (27.96±5.07 cM) and to thee locus (10.26±3.13 cM). Also, thePer-5 ande loci were located on the short arm of chromosome 2. In additionIdh-2 was also located on barley chromosome 2 and was linked to thev locus (13.18±3.56 cM), which is located on the long arm of chromosome 2. Two other marker genes,li andwst,,B, were linked (26.50±5.24 cM) on chromosome 2 but segregate independently of the other loci evaluated. This project was supported by funds from the U.S.-Spain Joint Committee for Scientific and Technological Cooperation.     

Polyamine-phospholipid interaction probed by the accessibility of the phospholipidsn-2 ester bond to the action of phospholipase A2

Summary Conditions were used where the action of porcine pancreatic phospholipase A2 on phospholipids can be followed in the absence of added calcium and the catalytic activity is supported by the calcium brought with the nanomolar enzyme. Therefore, alterations in the enzyme velocity resulting from the presence of spermine or spermidine could be specifically studied using 1-palmitoyl-2-(pyren-1-yl)hexanoyl-sn-glycero-3-phosphocholine (PPHPC) and 1-palmitoyl-2-(pyren-1-yl)hexanoyl-sn-glycero-3-phosphoglycerol (PPHPG) as substrates. Both spermine and spermidine activated the hydrolysis of PPHPG fourfold at polyamine/phospholipid molar ratios of approximately 11 and 121, respectively. Double-reciprocal plots of enzyme activityvs. PPHPG concentration revealed the enhancement to be due to increased apparentV _max while the apparentK _m was slightly increased. In the presence of 4mm CaCl₂ inhibition by polyamines of PPHPG hydrolysis by phospholipase A2 was observed. Using synthetic diamines we could further demonstrate that two primary amino groups are required for the activation. In the absence of exogenous CaCl₂ polyamines inhibited the hydrolysis of PPHPC by phospholipase A2. The presence of 4mm CaCl₂ reversed this inhibition and a twofold activation was observed at 10 m spermine. The results obtained indicate that the activation of PLA2 by spermine and spermidine is produced at the level of the substrate, PPHPG. This implies the formation of complexes of phosphatidylglycerol and polyamines with defined stoichiometries.     

Synthetic tools for adrenocorticotropin receptor identification

Biotinylated photoaffinity derivatives of adrenocorticotropin (ACTH) are potentially useful tools for the identification of ACTH receptors. The hormone can be attached covalently to its receptor by photoactivation, and the presence of biotin in the molecule facilitates isolation of the solubilized hormone-receptor complex on columns of immobilized succinoylavidin (Suc-avidin). Six photoprobes of ACTH1-24 have been prepared by reacting ACTH1-24, [25-biocytin]ACTH1-25 amide, and [25-dethiobiocytin]ACTH1-25 amide with either 4- or 5-azido-2-nitrophenylsulfenyl (4-NAPS and 5-NAPS, respectively) chlorides in acetic acid. The homogeneity of the photoprobes was carefully monitored by thin-layer chromatography and amino acid analyses of acid hydrolysates. The presence of underivatized starting material in the photoprobes was critically scrutinized by high-pressure liquid chromatography and was estimated to be less than 0.5%. Both the 4- and 5-NAPS derivatives stimulated maximal steroidogenesis (as compared with ACTH1-24) in calf adrenal cortical cells. However, the potencies of the two isomers differed significantly. The ED50 for steroidogenesis with 5-NAPS-ACTH1-24 was 100-fold greater than the standard (ACTH1-24) while that for 4-NAPS-ACTH1-24 was only approximately 7 times greater. Although 4-NAPS-ACTH1-24 was capable of stimulating maximal adenosine cyclic 3',5'-phosphate (cAMP) production, the 5-NAPS derivative was usually not. The level of stimulation with the 5-NAPS derivative varied considerably from cell preparation to cell preparation. ACTH1-24-induced cAMP production was inhibited by 5-NAPS-ACTH1-24 or 5-NAPS-[25-dethiobiocytin]ACTH1-25 amide.(ABSTRACT TRUNCATED AT 250 WORDS)     

Evolution and Extinction of Transposable Elements in Mendelian Populations

A model of the evolution of a transposable element family in a Mendelian host population is proposed that incorporates heritable phenotypic mutations in the elements. The temporal behavior of the numbers of mutant and wild-type elements is studied, and the expected extinction time of the transposable element family is examined. Our results indicate that, if the mutant can be transposed equally well in the presence of the wild type, then it can be expected to be found in preponderance, whereas elements, such as retroviruses, where the transposing genome and its phenotypic expression are coupled, may be characterized by a low mutant frequency.     

Evidence for the participation of disulfide and sulfhydril groups in the specific binding of [3H]prazosin in cerebral cortex

The tritiated ₁ antagonist prazosin [³H]PRZ binds specifically and with high affinity to postsynaptic adrenoceptors in membrane preparations from cerebral cortex. Since adrenoceptors are of protein nature, it was of interest of investigate the possible role of disulfide (—SS—) and sulfhydril (—SH) groups in the binding of [³H]PRZ. Pretreatment of the membranes with the disulfide and sulfhydryl reactivesdl0Dithiothreitol,l-Dithiothreitol, Dithioerythritol or 5,5-Dithiobis-(2-nitrobenzoic acid) (DTNB), alone or in combination with the alkylating agent N-Methylmaleimide (NMM), decreased specific [³HPRZ binding, with minor changes in the non-specific counts. Saturation experiments revealed that all these reagents reduced the affinity of the binding site for [³H]PRZ, as judged by theK _d 25°C, but only the alkylating agent NMM and the oxydizing reagent DTNB produced in addition to the increase inK _d, a decrease of the maximum binding capacity (B _max). The present results provide evidence for a participation of—SS—and/or—SH groups in the recognition site of the ₁-adrenoceptor of cerebral cortex.