苏云金芽胞杆菌幕虫亚种晶胞粘连现象与晶体蛋白基因cry26Aa所在质粒有关

苏云金芽胞杆菌幕虫亚种T02菌株的伴胞晶体在芽胞外壁内侧形成,呈现晶胞粘连的现象。在此菌株中克隆了cry26Aa和cry28Aa两个基因,并对晶胞粘连现象与质粒的相关性做了系统研究。通过消除幕虫亚种T02菌株的质粒,得到了仅消除cry26Aa所在质粒的菌株BMB1151和无质粒的菌株BMB1152。通过穿梭载体将cry26Aa和cry28Aa两个基因分别和同时转化无质粒突变株BMB1152并表达,形成的晶体与芽胞独立存在不能粘连,表明在幕虫亚种染色体背景下仅仅cry的表达不能形成晶胞粘连现象,从而推断晶胞粘连现象可能与幕虫亚种两个基因所在的质粒有关;进一步的研究发现将cry26Aa在仅消除cry26Aa所在质粒的突变株BMB1151中表达,形成的晶体与芽胞也分别独立存在不能粘连,从而进一步推断幕虫亚种晶胞粘连现象与cry26Aa所在质粒有关。     

Enzymatic synthesis of esters using an immobilized lipase

Various esters were synthesized in nearly anhydrous hexane from alcohols and carboxylic acids using a lipase from Candida cylindracea. The enzyme was immobilized on a nylon support and protein loadings as high as 10 mg/g were obtained. The activity of the immobilized enzyme was maximum in a range of temperatures from 25 to 37 degrees C. Ethylpropionate was formed from ethanol and propionic acid at a rate of 0.017 mol/h g immobilized protein. Different esters were formed at comparable rates and equilibrium conversions could generally be approached in less than 10 h in a batch reaction system. The immobilized lipase catalyst was quite stable and retained about one third of the initial activity after repeated experiments during the course of 72 days. A stirred tank continuous flow reactor was used successfully for the continuous production of esters.     

Multiple-rate components of axonally transported proteins in the hypothalamo-neurohypophysial system of the rat

The transport of labeled proteins from the hypothalamus to the neurohypophysis following 35S-methionine injection into the rat supraoptic nucleus was studied using a unique approach adapted for the study of short-axon systems. Multiple-rate components to those found in other neuronal systems were demonstrated. Neurosecretory vesicle-containing proteins (e.g., neurophysins) were transported at fast rates (greater than 120 mm/day), whereas the cytoskeletal protein, actin, moved principally in the slow component of transport. Two-dimensional gel electrophoresis was used to analyze the diverse patterns of labeled proteins found in the various rate components of axonal transport in this system.     

An approach to the study of intracellular proteins related to the excitability of the squid giant axon

The technique for covalently labeling proteins with 125I-labelled Bolton-Hunter reagent was used to determine the quantities of proteins released from the axoplasmic side of the squid axon membrane. The reagent could be introduced into the interior of the axon by the technique of intracellular perfusion, the radioiodination reaction being carried out in situ. Alternatively, the reaction could be carried out in vitro, i.e., by mixing the reagent with samples of proteins dissolved in the intracellular perfusion fluid collected from the axon. This technique was found to be sensitive enough to permit analysis of a large number of protein samples collected from a single axon. By the method of sodium dodecyl sulfate polyacrylamide gel electrophoresis, it was found that proteins of approx. 56 000 daltons were released into the perfusate when a solution of potassium chloride or potassium bromide was introduced into the interior of an axon. Suppression of axonal excitability was associated with this release of proteins. The significance of these findings in relation to the structure and function of the axon is discussed.     

A CALCIUM ACTIVATED PROTEASE IN SQUID AXOPLASM

Evidence for a protease in squid axoplasm which is selectively activated by Ca²⁺ and blocked by SH-inhibitors is presented. This protease appears to be particularly effective in degrading squid neurofilament proteins, but also extensively degrades various other major protein components in axoplasm.     

Synthesis of lovastatin with immobilized Candida rugosa lipase in organic solvents: Effects of reaction conditions on initial rates

Lipase from Candida rugosa immobilized on a nylon support has been used to synthesize lovastatin, a drug which lowers serum cholesterol levels, by the regioselective acylation of a diol lactone precursor with 2-methylbutyric acid in mixtures of organic solvents. Analogs of lovastatin having a different side chain were also obtained through this method by reacting the diol substrate with different carboxylic acids. The selection of reaction conditions that maximize the initial reaction rate is investigated. Since the diol substrate has very low solubility in non-polar solvents, reaction solvents consisting of mixtures of hexane with a different, more polar cosolvent are considered. For each of the cosolvent mixtures studied, the reaction rate is maximum for an intermediate percentage of cosolvent in hexane. With total concentrations of the diol lactone in the range 6.25-12.5 mM, maximum initial rates correspond approximately to those cosolvent concentrations that permit a complete solubilization of the substrate. At higher cosolvent concentrations, lower rates are obtained. When considering the same dissolved substrate concentration, the reaction rate was found to increase with increasing values of logP(mix) and decreasing values of the dielectric constant, when varying the composition of a binary solvent mixture. However, when comparing different cosolvents, no general trend with respect to these properties was observed. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56:671-680, 1997.     

Immunoprecipitation of an Affinity-Alkylated Fragment of the Muscarinic Acetylcholine Receptor with an Anti-Ligand Monoclonal Antibody

A monoclonal antibody raised against the muscarinic acetylcholine affinity-alkylating antagonist propylbenzilylcholine mustard was tested for its ability to recognize affinity-alkylated muscarinic receptors. We demonstrate here that although the antibody will not recognize the mustard when it is covalently linked to the native muscarinic receptor, trypsinization of affinity-labeled membranes releases a proteolytic labeled fragment that can be specifically immunoprecipitated by the antibody. Electrophoretic analysis of the immunoprecipitate indicates that the ligand was associated with a polypeptide of molecular weight 5,000. The recognition of this fragment by the antibody provides a means to immunopurify a portion of the muscarinic receptor that is at or near the ligand binding site.