Bacillus subtilis YhaM, a member of a new family of 3′-to-5′ exonucleases in gram-positive bacteria
Bacillus subtilis YhaM, a member of a new family of 3′-to-5′ exonucleases in gram-positive bacteria
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DOI：
10.1128/jb.184.22.6250-6259.2002
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发表时间：
2002-11-01
影响因子：
3.2
通讯作者：
Bechhofer, DH
中科院分区：
文献类型：
--
作者：
Oussenko, IA;Sanchez, R;Bechhofer, DH
利用一株缺乏3‘-5’-外切核糖核酸酶的枯草芽孢杆菌，用多核苷酸磷酸化酶(PNPase)和核糖核酸酶R纯化了由yhaM基因编码的另一种3‘-5’外切核糖核酸酶。YhaM在Mn2+(或Co2+)存在下具有活性，在Mg2+存在下不具有活性，也能降解单链DNA。缺失PNPase、RNase R和YhaM的突变体的整体mRNA半衰期与野生型没有显著差异，表明存在参与mRNA周转的额外活性。YhaM的序列同源物只在革兰氏阳性生物中发现。金黄色葡萄球菌的同源物CBF1也被证明是一种依赖于Mn2+的外切核糖核酸酶，它是参与质粒复制的双链DNA结合蛋白。YhaM蛋白有一个C-末端的“HD结构域”，存在于金属依赖的磷酸水解酶中。通过结构模拟表明，YhaM还含有一个N-末端的“OB-折叠”，存在于许多寡糖和寡核苷酸结合蛋白中。这两个领域的结合是独一无二的。因此，YhaM和来自革兰氏阳性生物的10个相关蛋白组成了一个新的核酸外切酶家族。
A strain of Bacillus subtilis lacking two 3'-to-5' exoribonucleases, polynucleotide phosphorylase (PNPase) and RNase R, was used to purify another 3'-to-5' exoribonuclease, which is encoded by the yhaM gene. YhaM was active in the presence of Mn2+ (or Co2+), was inactive in the presence of Mg2+, and could also degrade single-stranded DNA. The half-life of bulk mRNA in a mutant lacking PNPase, RNase R, and YhaM was not significantly different from that of the wild type, suggesting the existence of additional activities that can participate in mRNA turnover. Sequence homologues of YhaM were found only in gram-positive organisms. The Staphylococcus aureus homologue, CBF1, which had been characterized as a double-stranded DNA binding protein involved in plasmid replication, was also shown to be an Mn2+-dependent exoribonuclease. YhaM protein has a C-terminal "HD domain," found in metal-dependent phosphohydrolases. By structure modeling, it was shown that YhaM also contains an N-terminal "OB-fold," present in many oligosaccharide- and oligonucleotide-binding proteins. The combination of these two domains is unique. Thus, YhaM and 10 related proteins from gram-positive organisms constitute a new exonuclease family.