Three-dimensional structure and Molecular Evolution of Tandem repeals within Ice Nucleation Proteins

某些细菌使冰的结晶成核。冰核活性由蛋白质（冰核蛋白; INP）赋予。分子量接近120 kDa的INPs的氨基酸序列具有中心重复结构域（约占总序列的81%）。重复结构域由具有AxxxSxxx的共有序列的串联重复序列组成。INPs的结构仍然未知。本研究的目的是调查的演变和结构的INPs。首先，我们对10个INPs进行了详细的比较序列分析。分析表明，重复结构域分为四个亚结构域（R^c，R^1，R^2和R^N）。在此基础上，讨论了其演化历史。其次，我们对合成肽H-SGLRSVLTAGYGSSLISGRRSSLT-OH进行了相应于R^N亚结构域部分的NMR实验。NMR结果表明LTAGY序列中存在环状构象。

Certain bacteria nucleate the crystallization of ice. The ice-nucleation activity is conferred by a protein (ice nucleation protein ; INP). The amino acid sequences of the INPs with molecular weights near 120kDa have a central repeating domain (comprising approximately 81% of the total sequence). The repeating domain consists of tandem repeats with the consensus sequence of AxxxSxxx. The structure of the INPs is still unknown. The purpose of the present study is to investigate the evolution and the structure of the INPs. First, we performed, comparative sequence analysis of ten INPs in details. The analysis revealed that the repeating domain is separated into four subdomains (R^c, R^1, R^2 and R^N). On the basis of this result, the evolutionary history was discussed. Secondly, we performed NMR experiments of synthetic peptide H-SGLRSVLTAGYGSSLISGRRSSLT-OH corresponding to sections of the R^N subdomain. The NMR results indicated the presence of a loop conformation in the sequence of LTAGY.