Molecular and structural characterization of the HMP-AB gene encoding a pore-forming protein from a clinical isolate of Acinetobacter baumannii
Molecular and structural characterization of the HMP-AB gene encoding a pore-forming protein from a clinical isolate of Acinetobacter baumannii
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DOI：
10.1007/s00284-003-4050-4
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发表时间：
2003-11-01
影响因子：
2.6
通讯作者：
Katcoff, DJ
中科院分区：
文献类型：
--
作者：
Gribun, A;Nitzan, Y;Katcoff, DJ
鲍曼不动杆菌的主要外膜蛋白是热修饰蛋白HMP-AB，它是一种具有大孔径的孔蛋白，可以穿透分子量高达800 Da的溶质。戊二醛的交联实验没有显示单体之间的任何交联性，这一事实再次证明了这种孔蛋白作为单体孔蛋白的功能。该孔蛋白的比活性与其他单体孔蛋白相似。外膜的胰酶消化产生了一个23 kDa的HMP-AB蛋白片段，该片段对进一步的胰酶处理具有抵抗力。这一观察表明，HMP-AB以类似于单体孔蛋白的方式组装在膜中。克隆了HMP-AB基因，其开放阅读框为1038bp，编码346个氨基酸的蛋白质，计算的相对分子质量为35,636 Da。氨基酸序列和组成具有典型的革兰氏阴性菌孔蛋白：高度负的疏水性指数，没有疏水残基伸展，总电荷略负，不稳定指数低，甘氨酸含量高，没有半胱氨酸残基。HMP-AB与其他外膜蛋白的序列比较表明，HMP-AB与肠杆菌的外膜蛋白A(OmpA)和假单胞菌的外膜蛋白F(OprF)具有明显的同源性。二级结构分析表明，HMP-AB具有一个172个氨基酸的N-末端结构域和一个C-末端结构域，该结构域通过8个两亲性的β链跨越外膜，而C-末端结构域显然是一个锚定蛋白，与肽聚糖结合。结果还表明，HMP-AB属于外膜蛋白的8个跨膜β链家族。
The major outer membrane protein of Acinetobacter baumannii is the heat-modifiable protein HMP-AB, a porin with a large pore size allowing the penetration of solutes having a molecular weight of up to approximately 800 Da. Cross-linking experiments with glutardialdehyde failed to show any cross-linking between the monomers, a fact that proves again that this porin protein functions as a monomeric porin. The specific activity of this porin was found to be similar to that of other monomeric porins. Tryptic digestion of the outer membrane yielded a 23-kDa fragment of the HMP-AB protein that was resistant to further trypsin treatment. This observation indicates that HMP-AB is assembled in the membrane in a manner similar to monomeric porins. Cloning of the HMP-AB gene revealed an open reading frame of 1038 bp encoding a protein of 346 amino acids and a calculated molecular mass of 35,636 Da. The amino acid sequence and composition were typical of Gram-negative bacterial porins: a highly negative hydropathy index, absence of hydrophobic residue stretches, a slightly negative total charge, low instability index, high glycine content, and an absence of cysteine residues. Sequence comparison of HMP-AB with other outer membrane proteins revealed a clear homology with the monomeric outer membrane proteins, outer membrane protein A (OmpA) of Enterobacteria, and outer membrane protein F (OprF) of Pseudomonas sp. Secondary structure analysis indicated that HMP-AB has a 172-amino acid N-terminal domain that spans the outer membrane by eight amphiphilic beta strands and a C-terminal domain that apparently serves as an anchoring protein to the peptidoglycan layer. The results also indicate that HMP-AB belongs to the eight transmembrane beta-strand family of outer membrane proteins.