Tzfati Y, Abeliovich H, Avrahami D, Shlomai J
Department of Parasitology, Hebrew University, Hadassah Medical School, Jerusalem, Israel.
J Biol Chem. 1995 Sep 8;270(36):21339-45. doi: 10.1074/jbc.270.36.21339.
Replication of kinetoplast DNA minicircles of trypanosomatids initiates at a conserved 12-nucleotide sequence, termed the universal minicircle sequence (UMS, 5'-GGGGTTGGTGTA-3'). A single-stranded nucleic acid binding protein that binds specifically to this origin-associated sequence was purified to apparent homogeneity from Crithidia fasciculata cell extracts. This UMS-binding protein (UMSBP) is a dimer of 27.4 kDa with a 13.7-kDa protomer. UMSBP binds single-stranded DNA as well as single-stranded RNA but not double-stranded or four-stranded DNA structures. Stoichiometry analysis indicates the binding of UMSBP as a protein dimer to the UMS site. The five CCHC-type zinc finger motifs of UMSBP, predicted from its cDNA sequence, are similar to the CCHC motifs found in retroviral Gag polyproteins. The remarkable conservation of this motif in a family of proteins found in eukaryotic organisms from yeast and protozoa to mammals is discussed.
锥虫动质体DNA微环的复制起始于一个保守的12核苷酸序列，称为通用微环序列（UMS，5'-GGGGTTGGTGTA-3'）。从法氏克氏锥虫细胞提取物中纯化出一种与该起始相关序列特异性结合的单链核酸结合蛋白，达到了表观均一性。这种UMS结合蛋白（UMSBP）是一个由27.4 kDa组成的二聚体，其单体为13.7 kDa。UMSBP能结合单链DNA以及单链RNA，但不结合双链或四链DNA结构。化学计量分析表明UMSBP作为一种蛋白质二聚体与UMS位点结合。根据其cDNA序列预测，UMSBP的五个CCHC型锌指基序与逆转录病毒Gag多聚蛋白中的CCHC基序相似。本文讨论了在从酵母、原生动物到哺乳动物的真核生物中发现的一类蛋白质中该基序的显著保守性。
