Cassago A, Rodrigues E M, Prieto E L, Gaston K W, Alfonzo J D, Iribar M P, Berry M J, Cruz A K, Thiemann O H
Instituto de Física de São Carlos, Universidade de São Paulo, Caixa Postal 369, 13560-590 São Carlos, SP, Brazil.
Mol Biochem Parasitol. 2006 Oct;149(2):128-34. doi: 10.1016/j.molbiopara.2006.05.002.
Selenoproteins result from the incorporation of selenocysteine (Sec-U) at an UGA-stop codon positioned within a gene's open reading frame and directed by selenocysteine insertion sequence (SECIS) elements. Although the selenocysteine incorporation pathway has been identified in a wide range of organisms it has not yet been reported in the Kinetoplastida Leishmania and Trypanosoma. Here we present evidence consistent with the presence of a selenocysteine biosynthetic pathway in Kinetoplastida. These include the existence of SECIS-containing coding sequences in Leishmania major and Leishmania infantum, the incorporation of (75)Se into Leishmania proteins, the occurrence of selenocysteine-tRNA (tRNA (sec) (uca)) in both Leishmania and Trypanosoma and in addition the finding of all genes necessary for selenocysteine synthesis such as SELB, SELD, PSTK and SECp43. As in other eukaryotes, the Kinetoplastids have no identifiable SELA homologue. To our knowledge this is the first report on the identification of selenocysteine insertion machinery in Kinetoplastida, more specifically in Leishmania, at the sequence level.
硒蛋白是由硒代半胱氨酸（Sec-U）掺入位于基因开放阅读框内的UGA终止密码子，并由硒代半胱氨酸插入序列（SECIS）元件指导而产生的。尽管硒代半胱氨酸掺入途径已在多种生物体中得到鉴定，但尚未在动质体目（锥虫纲）的利什曼原虫和锥虫中报道。在此，我们提供的证据表明动质体目中存在硒代半胱氨酸生物合成途径。这些证据包括在硕大利什曼原虫和婴儿利什曼原虫中存在含SECIS的编码序列、将（75）Se掺入利什曼原虫蛋白质中、在利什曼原虫和锥虫中均存在硒代半胱氨酸转运RNA（tRNA（sec）（uca）），此外还发现了硒代半胱氨酸合成所需的所有基因，如SELB、SELD、PSTK和SECp43。与其他真核生物一样，动质体目没有可识别的SELA同源物。据我们所知，这是关于在动质体目，更具体地说是在利什曼原虫中，在序列水平上鉴定硒代半胱氨酸插入机制的首次报道。
