Fraij B M, Gonzales R A
Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater 74078, USA.
Biochim Biophys Acta. 1996 Apr 10;1306(1):63-74. doi: 10.1016/0167-4781(95)00219-7.
A 2.4 kilobase (kb) cDNA encoding a new form of human tissue transglutaminase homologue (TGH2) was isolated from retinoic acid-induced human erythroleukemia cell (HEL) library. Full-length cDNA analysis gives an open reading frame coding for a polypeptide of 349 amino acid residues with a molecular mass of 38,700 Da. This variant differs from the previously reported homologue TGH in that it is 199 amino acids shorter and has an alternative, 63 amino acid COOH-terminal peptide. The 3'-untranslated region of the cDNA also differs from the previously reported sequences for both TGH and human tissue transglutaminase. The region coding for the first 286 amino acids of TGH2, which contains the active site is identical to TGH. Immunoprecipitation of the in vitro translation product from a synthetic TGH2 mRNA and immunoprecipitation of total protein of human heart, liver, kidney and cultured erythroleukemia HEL cell, revealed a protein with a molecular mass of 37,000 Da by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Comparison of the cDNA sequence for the previously known tissue transglutaminases with genomic DNA and the TGH2 cDNA described here indicate that the sequence divergence points correlate with known intron-exon boundaries. The smaller RNA species encode for truncated proteins with novel carboxyl termini. The TGH cDNA and the TGH2 cDNA both produce transcripts which start with the regular coding sequence for TGase and then fail to splice at specific donor sites, resulting in the use of an alternative exon that contains a stop codon.
从视黄酸诱导的人红白血病细胞（HEL）文库中分离出一个编码新型人组织转谷氨酰胺酶同源物（TGH2）的2.4千碱基（kb）cDNA。全长cDNA分析得到一个开放阅读框，编码一个由349个氨基酸残基组成的多肽，分子量为38,700道尔顿。这个变体与先前报道的同源物TGH不同，它短199个氨基酸，并且有一个不同的、63个氨基酸的COOH末端肽。该cDNA的3'-非翻译区也与先前报道的TGH和人组织转谷氨酰胺酶的序列不同。编码TGH2前286个氨基酸的区域包含活性位点，与TGH相同。对合成的TGH2 mRNA的体外翻译产物进行免疫沉淀，以及对人心脏、肝脏、肾脏和培养的红白血病HEL细胞的总蛋白进行免疫沉淀，通过十二烷基硫酸钠-聚丙烯酰胺凝胶电泳显示出一种分子量为37,000道尔顿的蛋白质。将先前已知的组织转谷氨酰胺酶的cDNA序列与基因组DNA以及此处描述的TGH2 cDNA进行比较表明，序列差异点与已知的内含子-外显子边界相关。较小的RNA种类编码具有新羧基末端的截短蛋白。TGH cDNA和TGH2 cDNA都产生转录本，这些转录本从TGase的常规编码序列开始，然后在特定的供体位点未能剪接，导致使用一个包含终止密码子的替代外显子。
