Company R, Calduch-Giner J A, Mingarro M, Pérez-Sánchez J
Instituto de Acuicultura de Torre de la Sal (CSIC), Castellón, Spain.
Comp Biochem Physiol B Biochem Mol Biol. 2000 Oct;127(2):183-92. doi: 10.1016/s0305-0491(00)00250-9.
Three cDNA clones encoding for European sea bass somatolactin (SL) were obtained by RT-PCR and 3' RACE of RNA of pituitary origin. Clone 1 was 582 bp in length, and included a part of the signal peptide and the 5' end of the mature protein. Clone 2 (1075 bp) included a fragment of the coding sequence and the 3' untranslated region, which was 888 bp in length and contained two putative polyadenylation signals (AATAAA) at 12-17, and 202-207 nucleotides upstream of the poly (A) tail. Clone 3 was 624 bp in length and its nucleotide sequence encoding for the entire mature protein confirmed the sequence already determined from the first two clones. The size of SL mRNA transcripts was estimated by Northern blot analysis and a single band of approximately 1.6 kb was observed with pituitary RNAs. No band was found with RNAs of brain and liver origin. Alignment of the deduced amino acid sequence revealed that European sea bass SL shared 90-84% identity with perciform, pleuronectiform and scorpaeniform fish SLs, and 77-57% with other SLs of more distant fish orders, with a strict conservation of Cys residues and the N-glycosylation site (Asn-Lys-Thr) at 121-123 amino acid positions. The reconstruction of the phylogenetic tree based on SL nucleotide sequences. and analyzed by maximum likelihood distances, showed the same clustering as the present hierarchy of fish. When comparisons were made among SL, prolactin and growth hormone of European sea bass, the overall amino identity was relatively low (22-23%). However, a high degree of amino acid homology was found at the C-terminus, which contains three of the four Cys residues strictly conserved in all the members of GH/PRL family.
通过对垂体来源的RNA进行逆转录聚合酶链反应（RT-PCR）和3'端快速扩增cDNA末端（3' RACE），获得了三个3个三种编码欧洲鲈鱼生长抑素（SL）的cDNA克隆。克隆1长度为582 bp，包含信号肽的一部分和成熟蛋白的5'端。克隆2（1075 bp）包含编码序列片段和3'非翻译区，其长度为888 bp，在多聚腺苷酸（A）尾上游12 - 17和202 - 207个核苷酸处含有两个推定的聚腺苷酸化信号（AATAAA）。克隆3长度为624 bp，其编码整个成熟蛋白的核苷酸序列证实了前两个克隆已确定的序列。通过Northern印迹分析估计了SL mRNA转录本的大小，在垂体RNA中观察到一条约1.6 kb的单带。在脑和肝脏来源的RNA中未发现条带。推导的氨基酸序列比对显示，欧洲鲈鱼SL与鲈形目、鲽形目和鲉形目鱼类的SL具有90 - 84%的同一性，与更远亲缘关系鱼类目其他SL具有77 - 57%的同一性，在121 - 123个氨基酸位置的半胱氨酸残基和N - 糖基化位点（Asn - Lys - Thr）严格保守。基于SL核苷酸序列重建的系统发育树，并通过最大似然距离分析，显示出与当前鱼类分类相同的聚类。当对欧洲鲈鱼的SL、催乳素和生长激素进行比较时，总体氨基酸同一性相对较低（22 - 23%）。然而，在C末端发现了高度的氨基酸同源性，该末端包含在GH/PRL家族所有成员中严格保守的四个半胱氨酸残基中的三个。
