Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, India.
Acta Biochim Biophys Sin (Shanghai). 2010 Jan;42(1):58-69. doi: 10.1093/abbs/gmp105.
We examined whether C-terminal residues of soluble recombinant FtsZ of Mycobacterium tuberculosis (MtFtsZ) have any role in MtFtsZ polymerization in vitro. MtFtsZ-deltaC1, which lacks C-terminal extreme Arg residue (underlined in the C-terminal extreme stretch of 13 residues, DDDDVDVPPFMRR), but retaining the penultimate Arg residue (DDDDVDVPPFMR), polymerizes like full-length MtFtsZ in vitro. However, MtFtsZ-deltaC2 that lacks both the Arg residues at the C-terminus (DDDDVDVPPFM), neither polymerizes at pH 6.5 nor forms even single- or double-stranded filaments at pH 7.7 in the presence of 10 mM CaCl(2). Neither replacement of the penultimate Arg residue, in the C-terminal Arg deletion mutant DDDDVDVPPFMR, with Lys or His or Ala or Asp (DDDDVDVPPFMK/H/A/D) enabled polymerization. Although MtFtsZ-deltaC2 showed secondary and tertiary structural changes, which might have affected polymerization, GTPase activity of MtFtsZ-deltaC2 was comparable to that of MtFtsZ. These data suggest that MtFtsZ requires an Arg residue as the extreme C-terminal residue for polymerization in vitro. The polypeptide segment containing C-terminal 67 residues, whose coordinates were absent from MtFtsZ crystal structure, was modeled on tubulin and MtFtsZ dimers. Possibilities for the influence of the C-terminal Arg residues on the stability of the dimer and thereby on MtFtsZ polymerization have been discussed.
我们研究了结核分枝杆菌（Mycobacterium tuberculosis）可溶性重组 FtsZ 的 C 末端残基是否在体外 FtsZ 聚合中发挥作用。MtFtsZ-deltaC1 缺乏 C 末端极端的精氨酸残基（在 13 个残基的 C 末端极端伸展部分下划线，DDDDVDVPPFMRR），但保留倒数第二个精氨酸残基（DDDDVDVPPFMR），在体外像全长 MtFtsZ 一样聚合。然而，MtFtsZ-deltaC2 既缺乏 C 末端的两个精氨酸残基（DDDDVDVPPFM），也不能在 pH6.5 下聚合，也不能在 pH7.7 下即使在 10mM CaCl2 存在下形成单链或双链丝状。用赖氨酸、组氨酸或丙氨酸或天冬氨酸（DDDDVDVPPFMK/H/A/D）替代 C 末端精氨酸缺失突变体 DDDDVDVPPFMR 中的倒数第二个精氨酸残基，均不能促进聚合。虽然 MtFtsZ-deltaC2 显示出二级和三级结构的变化，这可能影响了聚合，但 MtFtsZ-deltaC2 的 GTPase 活性与 MtFtsZ 相当。这些数据表明，MtFtsZ 要求 C 末端的精氨酸作为极端残基才能在体外聚合。包含 C 末端 67 个残基的多肽片段，其坐标在 MtFtsZ 晶体结构中缺失，根据微管蛋白和 MtFtsZ 二聚体进行建模。讨论了 C 末端精氨酸残基对二聚体稳定性的影响，进而对 MtFtsZ 聚合的影响。
