Sheppard D, Rozzo C, Starr L, Quaranta V, Erle D J, Pytela R
Lung Biology Center, San Francisco, CA 94143.
J Biol Chem. 1990 Jul 15;265(20):11502-7.
The integrin family of adhesion receptors consists of several heterodimeric glycoproteins, each composed of one alpha and one beta subunit. Three different mammalian beta subunits, beta 1, beta 2, and beta 3, have been sequenced, but recent evidence suggests the existence of several others. Amplification of guinea pig airway epithelial cell cDNA with oligonucleotide primers designed to recognize consensus integrin beta subunit sequences led to the identification of a novel partial cDNA sequence. Clones containing portions of this sequence were used to screen cDNA libraries constructed from the human pancreatic carcinoma cell line FG-2 and identified a series of overlapping clones encoding the full-length sequence of the human homologue of this protein. This sequence of 788 amino acids is 43, 38, and 47% identical to the sequences of beta 1, beta 2, and beta 3, respectively. Features shared between this novel protein and the previously sequenced beta subunits include the positions of all 56 cysteine residues in the extracellular domain, the single putative transmembrane domain, and the short putative cytoplasmic domain. However, a unique 11-amino acid extension at the carboxyl terminus, not present in any of the other beta subunits, is suggestive of distinctive interactions with cytoplasmic components. Comparison of the human and guinea pig sequences reveals a high degree (94%) of cross-species conservation. Because this protein is clearly distinct from the two other recently described integrins beta 4 and beta 5, we propose to designate it beta 6.
黏附受体的整合素家族由几种异二聚体糖蛋白组成，每个异二聚体由一个α亚基和一个β亚基组成。已对三种不同的哺乳动物β亚基β1、β2和β3进行了测序，但最近的证据表明还存在其他几种亚基。用设计用于识别共有整合素β亚基序列的寡核苷酸引物扩增豚鼠气道上皮细胞cDNA，从而鉴定出一种新的部分cDNA序列。含有该序列部分的克隆用于筛选由人胰腺癌细胞系FG-2构建的cDNA文库，并鉴定出一系列编码该蛋白人同源物全长序列的重叠克隆。这个由788个氨基酸组成的序列分别与β1、β2和β3的序列有43%、38%和47%的同源性。这种新蛋白与先前测序的β亚基共有的特征包括细胞外结构域中所有56个半胱氨酸残基的位置、单个推定的跨膜结构域和短的推定细胞质结构域。然而，在羧基末端有一个独特的11个氨基酸的延伸，这在任何其他β亚基中都不存在，提示其与细胞质成分有独特的相互作用。人和豚鼠序列的比较显示出高度的（94%）跨物种保守性。由于这种蛋白明显不同于最近描述的另外两种整合素β4和β5，我们建议将其命名为β6。
