OKP-B-13型β-内酰胺酶的克隆与表达

目的构建OKP-B-13型β-内酰胺酶的表达载体。方法抽提菌株的质粒,应用PCR扩增OKP-B-13基因全长编码序列,扩增产物经Nde I、Xho I酶切后连接至pET-26b(+)表达载体,重组质粒经酶切及DNA测序确证后,转入大肠埃希菌BL21(DE3),IPTG诱导表达。超声破碎法提取表达蛋白产物,检测其活性,等电聚焦电泳检测蛋白的等电点(pI)。结果PCR扩增获得879 bp的产物,重组表达载体经Nde I、Xho I酶切及DNA测序后表明,目的基因已成功接入表达载体,重组菌的粗提物经头孢硝噻吩检测显示具有β-内酰胺酶活性,显示载体[pET-26b(+)/OKP-B-13]构建成功。目的等电点为7.1。结论β-内酰胺酶OKP-B-13在原核表达细胞中实验了基因重组表达,为进一步分析酶的特性提供条件。     

What Amino Acid Properties Affect Protein Evolution?

We studied 10 protein-coding mitochondrial genes from 19 mammalian species to evaluate the effects of 10 amino acid properties on the evolution of the genetic code, the amino acid composition of proteins, and the pattern of nonsynonymous substitutions. The 10 amino acid properties studied are the chemical composition of the side chain, two polarity measures, hydropathy, isoelectric point, volume, aromaticity, aliphaticity, hydrogenation, and hydroxythiolation. The genetic code appears to have evolved toward minimizing polarity and hydropathy but not the other seven properties. This can be explained by our finding that the presumably primitive amino acids differed much only in polarity and hydropathy, but little in the other properties. Only the chemical composition (C) and isoelectric point (IE) appear to have affected the amino acid composition of the proteins studied, that is, these proteins tend to have more amino acids with typical C and IE values, so that nonsynonymous mutations tend to result in small differences in C and IE. All properties, except for hydroxythiolation, affect the rate of nonsynonymous substitution, with the observed amino acid changes having only small differences in these properties, relative to the spectrum of all possible nonsynonymous mutations. Received: 2 January 1998 / Accepted: 25 April 1998     

Application of isoelectric focusing for studies of major histocompatibility complex class I antigen expression on human carcinomas and sarcomas

Summary By one-dimension isoelectric focusing we analysed the major histocompatibility complex class I antigen expression on human tumours. Blood lymphocytes of the patients, processed in parallel, served as a basis for comparison. The prerequisite for the analysis is the preparation of metabolically active tumour cell suspensions devoid of significant leucocyte contamination. The method was found to be suitable for study of the expression of HLA alleles on ex vivo tumour cells and allowed the detection of changes imposed by in vitro treatment with interferon and tumour necrosis factor .     

Isoelectric focusing of phosphorylated cattle rhodopsin

³²P-rhodopsin was partially separated by isoelectric focusing into several fractions of different phosphorylation extent. It was found that the incorporated phosphate is not uniformly distributed in a population of rhodopsin molecules. In a preparation with an average phosphorylation extent of 2.4 moles of phosphate per mole of rhodopsin, most of the ³²P-phosphate was found in fractions where 4–5 phosphates are bound per rhodopsin, whereas a large fraction of the total rhodopsin was not phosphorylated at all. The maximum number of phosphate binding sites in rhodopsin appears to be at least five.Abbreviations used P/Rh moles of phosphate per mole of rhodopsin - ROS rod outer segments Presented in part at the EMBO workshop on Transduction Mechanism of Photoreceptors, held in Jülich, Germany, on 4–8 October, 1976     

Schistosoma mansoni: Purification and characterization of malate dehydrogenases

Isoelectric focusing of a homogenate of Schistosoma mansoni, followed by malate dehydrogenase-specific staining, showed the presence of two major and five minor malate dehydrogenase isoenzymes (EC 1.1.1.37), with isoelectric points ranging from 7.3 to 9.5. The malate dehydrogenase isoenzymes were purified by gel filtration, followed by ion-exchange chromatography on DEAE- and CM-cellulose. The isoenzymes could be differentiated by their susceptibility to substrate inhibition. No differences in the Michaelis-Menten constants for substrate were found. One of the isoenzymes is inhibited by 5′-AMP. Further purification of this particular isoenzyme was achieved by affinity chromatography on 5′-AMP-Sepharose 4B. Analysis after subcellular fractionation indicated a mitochondrial origin for this isoenzyme. The mitochondrial isoenzyme (at a recovery of 80%) was purified 218-fold compared to the crude soluble extract, and contained about 40% of the total malate dehydrogenase activity. The enzyme has a molecular weight of 65,500 and showed absolute specificity for l-malic acid, NAD, and NADH. The final preparation has a specific activity of 451 U/mg protein. Physicochemical studies, including binding constants, substrate inhibition, thermostability, and pH optima, demonstrated differences between the mitochondrial and cytoplasmic enzymes. A role for malate dehydrogenase in Schistosoma mansoni metabolism is discussed.     

Discrimination between closed and open forms of lipases using electrophoretic techniques

The enhanced catalytic activity of lipases is often associated with structural changes. The three-dimensional (3D) structures showed that the covalently inhibited lipases exist under their open conformations, in contrast to their native closed forms. We studied the inhibition of various lipases--human and dog gastric lipases, human pancreatic lipase, and Humicola lanuginosa lipase--by the octyl-undecyl phosphonate inhibitor, and we measured the subsequent modifications of their respective electrophoretic mobility. Furthermore, the experimental values of the isoelectric points found for the native (closed) and inhibited (open) lipases are in agreement with theoretical calculations based on the electrostatic potential. We concluded that there is a significant difference in the isoelectric points between the closed (native) and open (inhibited) conformations of the four lipases investigated. Thus, analysis of the electrophoretic pattern is proposed as an easy experimental tool to differentiate between a closed and an open form of a given lipase.     

Differences in the envelope proteins ofChlamydia pneumoniae,Chlamydia trachomatis,andChlamydia psittaci shown by two-dimensional gel electrophoresis

Analysis by two-dimensional gel electrophoresis of theN-laurylsarkosinate(Sarkosyl)-insoluble envelope complexes ofl-^[35]S-cysteine-iabeled elementary bodies ofChlamydia pneumoniae strain IOL-207,Chlamydia trachomatis serovar LGV2, D, and F, andChlamydia psittaci strain 6BC showed differences in the molecular charges of chlamydial outer membrane proteins. The apparent isoelectric point (pI) of the major outer membrane protein ofC. pneumoniae strain IOL-207 was 6.4, whereas the pI of the major outer membrane protein of theC. trachomatis andC. psittaci strains differed little from one another, ranging from 5.3 to 5.5. The 60-kDa cysteinerich protein ofC. pneumoniae was the only 60-kDa chlamydial protein with a pI value (5.9) more acidic than that of the corresponding major outer membrane protein. As a general rule, the charges of both the 60-kDa and the lowmolecular-mass (12–15 kDa) cysteine-rich proteins were widely variable, depending on the strain. However, in cach individual strain, the variation of the charge of the 60-kDa protein had a compensatory change in the lowmolecular-mass cysteine-rich protein.     

The semidwarf gene,sd-1, of rice (Oryza sativa L.). I. Linkage with the esterase locus,Estl-2

The linkage relationship between the semidwarf gene (sd-1) and the isozyme locus EstI-2 was elucidated using segregating populations derived from crosses between several semidwarf testers and tall rice varieties. Bimodal distributions for culm length were observed in F₂ populations of three cross combinations, including Shiokari/Shiokari (sd-1), Taichung 65 (A,Pn,Pau)/Taichung 65 (sd-1), and Milyang 23/Kasalath. Taking the valley of the distribution curves as the dividing point, two height classes were apparent with a segregation ratio of 3 tall1 short, demonstrating this character to be under the control of a single recessive gene. An inheritance study of esterase isozymes, based on isoelectric focusing (IEF), showed that the EstI-2 locus had two active allozymes of monomeric structure and one null form, which were designated a, b, and n, respectively (Eun et al. 1990). Semidwarf testers such as Shiokari (sd-1), Taichung 65 (sd-1) and Milyang 23 have an active allozyme designated as EstI-2^aa, while the tall parents, Shiokari and Taichung 65 (A,Pn,Pau), have the active allozyme, EstI-2^bb, and Kasalath has a null form of the allozyme, EstI-2ⁿⁿ. By dividing F₂ populations based on EstI-2 allozyme patterns, culmlength distributions exhibited trimodal curves. Most of the short plants had the homozygous EstI-2^aa pattern of the short parents, most of the tall plants had the homozygous pattern, EstI-2^bb or EstI-2ⁿⁿ, and most of the intermediate plants had the heterozygous EstI-2^ab or EstI-2^an banding pattern. Einkage analysis indicated that sd-1 and EstI-2 were tightly linked. These findings were also confirmed by segregation analyses in F₃ progenies. No recombinants among 171 F₃ families from the Shiokari/Shiokari (sd-1) combination, five recombinants among 267 F₃ families from Taichung 65 (A,Pn,Pau)/Taichung 65(sd-1), and only two recombinants out of 237 F₃ families from Milyang 23/Kasalath, were found. The recombination values were 0, 1.87 and 0.8%, respectively.     

Blood genetic markers in the Chinese of two eastern provinces

A total of 205 Han Chinese from two eastern provinces (155 from Fujien and 50 from Hopeh) were tested for the distribution of six blood groups--A1A2BO, MN, Rhesus (CcDEe), Lewisa, Kell (Kk) and Fya--four serum proteins--albumin and haptoglobin types; transferrin and group-specific component subtypes--haemoglobin, and twelve red cell enzyme systems--glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, lactate and malate dehydrogenases; acid phosphatase, esterate-D, glyoxalase I, adenylate kinase, glucose-phosphate isomerase, phosphoglucomutase (locus 2), and superoxide dismutase types; and phosphoglucomutase (locus 1) subtypes. The frequencies of blood groups were more or less within the reported frequencies in the Chinese. However the frequency of le was much lower in the present series. The Chinese are characterized by low p1, Ro, k, le, and a high Fya in general. P2 was lacking in the Chinese. There were some differences in the blood group frequencies in the two provinces. The frequencies of Hp alleles; Tf and Gc subtypes show characteristic mongoloid features with high Hp1, TfD, and GcIF. The frequency of TFC2 was higher in the Fujien province than that in Hopeh. At the hemoglobin locus only one Hb AD was detected, while the frequency of the beta-thalassemia trait was 0.03. No red cell G6PD deficiency or variant was detected. The distribution of red cell enzymes showed Mongoloid characteristics with low PGDC, AK2, ESD1, GLO1, and higher pa. PGM1 subtypes also had Mongoloid characteristics with lower PGM2+ and higher PGM2-. The phenotypic distribution of all the fifteen polymorphic loci was at Hardy-Weinberg equilibrium in both the Chinese populations.     

The major gut esterase locus in the nematode Caenorhabditis elegans

Summary Mutations in the major gut esterase of the nematode Caenorhabditis elegans have been induced by ethylmethane sulfonate and detected by isoelectric focusing. The gut esterase locus, denoted ges-1, maps less than 0.3 map units to the right of the unc-60 locus, at the left end of chromosome V.