核苷酸酸酶和亞硫酸基轉移酵素之間的結構與序列關係

Abstract

本篇論文之研究動機，係來自於文獻中曾提到：亞硫酸基轉移酵素與核苷酸激酶在結構上非常相似，其方均根誤差值（rmsd）小於4Å。為了研究與釐清亞硫酸基轉移酵素與核苷酸激酶之間，結構與序列的關係，在本篇論文中，我們研究亞硫酸基轉移酵素與核苷酸激酶的序列相似度與結構相似度。首先，我們依據鹼基的不同，將核苷酸激酶分組成五組，即A、T、C、G、U五組，並將亞硫酸基轉移酵素歸類為額外一組；因此，總共有六組蛋白質。接著，我們分析這六組蛋白質在組內之序列相似度與方均根誤差值的關係，並比較20種胺基酸在各個蛋白質中所佔的比例。然後，以同樣的方法，分析亞硫酸基轉移酵素與各組核苷酸激酶之序列相似度與方均根誤差值的關係，及20種胺基酸佔有的比例。我們發現各組內的序列相似度皆大於25%，其方均根誤差值均小於4Å，至於亞硫酸基轉移酵素與各組核苷酸激酶的序列相似度，則均小於20%，其方均根誤差值在4 Å左右。由此可知，亞硫酸基轉移酵素與各組核苷酸激酶的序列與結構之間是沒有關係的。

This research is motivated by the statements in literature, that the structures of sulfotransferases and nucleotide kinases are very similar and their rmsds are less than 4Å.To study and clarify the relationships of the structure between sulfotransferases and nucleotide kinases, in this thesis, we analyze the relationshi of structures and sequences between nucleotide kinases and sulfotransferases. We first divided nucleotide kinases into 5 groups, A, T, C, G, U, according to their difference in nucleosides, and considered sulfotransferases as an additional one. Hence, there are totally 6 groups of proteins. We then analyzed sequence identities, calculated rmsds for proteins, and compared the percentage of each amino acid for the proteins of each group. We also applied the same scheme to obtain sequence identities and rmsds between sulfotransferases and each nucleotide kinase. Our results showed that all the proteins with in each group had sequence identities greater than 25%, and rmsds less than 4Å. However, between sulfotransferases and each group of nucleotide kinases, sequence identities are less than 20% and rmsds are roughly 4Å. Accordingly, there is no significant relationship in the sequences and structures between sulfotransferases and nucleotide kinases.