噬菌体裂解酶研究进展

噬菌体裂解酶是双链DNA噬菌体所特有的细胞壁水解酶。研究表明,所有噬菌体裂解酶在结构上具有相似性,即含有2个结构域：比较保守的N端催化区和差异较大的C端特异性结合区。裂解酶的高亲和性与种属特异的细胞壁糖基有关,而后常常是细菌存活的必要成分。所以,细菌难以产生对裂解酶的抗性。本简要综述噬茵体裂解酶的研究进展。     

分支杆菌噬菌体D29 Lysin B的表达、纯化及酶学性质分析

克隆表达噬菌体D29 LysinB(LysB)并对其酶学性质进行研究。以噬菌体D29基因组为模板,用PCR方法扩增lysB基因,与表达载体pET22b连接,将重组质粒转化至Escherichiacoli BL21(DE3)中表达,镍柱亲和层析(Ni-NTA)纯化可溶性表达产物,并对重组蛋白的活性进行分析检测。结果表明:成功构建了pET22b-lysB表达载体,并从1L的LB培养物中获得了33.2mg高纯度重组蛋白(His-LysB);His-LysB具有分解脂肪的能力,属于脂肪酶;生物化学特性分析表明:丁酸对硝基苯(pNPB)为水解底物,His-LysB热稳定性不佳,30℃以下比较稳定,随着温度的升高,稳定性逐渐降低;该蛋白具有较高的pH值适应性,pH5.0~9.5范围内稳定性较高;在23℃和pH7.5时酶活力最高,其比酶活为1.3U/mg;金属离子Zn2+、Cu2+、Mg2+、Mn2+和苯甲基磺酰氟(PMSF)抑制剂对酶活具有强烈的抑制作用。本研究为开发新的治疗结核药物提供了一个新的选择。     

Characterization of a sperm lysin of Volvox carteri

Summary A cell-wall degrading enzyme has been isolated from mature sperm packets of the green flagellate Volvox carteri (Poona strain). This sperm lysin (S-lysin) is a Ca²⁺-dependent protease of 34 kDa with an essential serine group in its active centre. Neither SH group-blocking reagents nor transition metal chelators inhibit its action. S-lysin degrades the hydroxyproline-rich glycoprotein structures of the cell walls of sheath cells and gonidia (eggs) of vegetative and sexual spheroids in a characteristic manner. In asexual spheroids the somatic envelope is totally disintegrated, whereas in sexual spheroids pores are formed by local lysis at sites of adjacent eggs. Although S-lysin is very similar to the G-lysin of the closely related Chlamydomonads, it is species specific and does not attack the mother or daughter cell walls of Chlamydomonas reinhardtii. S-lysin resembles the aerosin of animal sperm cells in some aspects of its action.Dedicated to Professor Richard C. Starr on the occasion of his 65th birthday. He called the piper and gave the tune     

Engineering active lysostaphin variants that incorporate noncanonical amino acids and characterizing the effects of site-specific PEGylation

We describe a facile strategy to identify sites for the incorporation of noncanonical amino acids into lysostaphin—an enzyme that degrades the cell wall of Staphylococcus aureus—while retaining stapholytic activity. We used this strategy to generate active variants of lysostaphin incorporating para-azidophenylalanine. The incorporation of this “reactive handle” enabled the orthogonal site-specific modification of the enzyme variants with polyethylene glycol (PEG) using copper-free click cycloaddition. PEGylated lysostaphin variants could retain their stapholytic activity, with the extent of retention depending on the site of modification and the PEG molecular weight. The site-specific modification of lysostaphin could be useful not only for PEGylation to improve biocompatibility but also for the incorporation of the enzyme into hydrogels and other biomaterials and for studies of protein structure and dynamics. Moreover, the approach described herein could be readily applied to identify suitable sites for the incorporation of reactive handles into other proteins of interest.