Suzuki S, Huang Z S, Tanihara H
Department of Ophthalmology, University of Southern California School of Medicine, Los Angeles.
Proc Natl Acad Sci U S A. 1990 Jul;87(14):5354-8. doi: 10.1073/pnas.87.14.5354.
cDNAs for another beta subunit of the integrin family were isolated with the aid of polymerase chain reaction and sequenced. The combined cDNA sequence is 3110 base pairs (bp) in size and has one long open reading frame of 2388 bp. The deduced amino acid sequence is similar to those of other integrin beta subunits but does not correspond to beta 1, beta 2, beta 3, or beta 4 subunits. This beta subunit is divided by a membrane-spanning domain into a large extracellular domain at the N-terminal side and a small intracellular domain at the C-terminal side. The extracellular domain has a cysteine-rich region that contains four repeats of 8-cysteine motifs. All 56 cysteine residues found in the extracellular domains of other mature beta subunits are present in this beta subunit. The beta subunit reported here has particularly high homology with the beta 3 subunit. The mRNA for the molecule is approximately 3.5 kbp in size and is expressed in various cell types. Other researchers have recently reported additional beta subunits that associate with the vitronectin receptor alpha subunit. The deduced amino acid sequence of this molecule contains the N-terminal partial amino acid sequence of one of these beta subunits, beta x. The beta subunit described herein seems to be identical to the beta x subunit and to function as the beta subunit of a vitronectin receptor.
借助聚合酶链反应分离出整合素家族另一个β亚基的互补DNA（cDNA）并进行测序。合并后的cDNA序列大小为3110个碱基对（bp），有一个2388 bp的长开放阅读框。推导的氨基酸序列与其他整合素β亚基的序列相似，但与β1、β2、β3或β4亚基不对应。这个β亚基被一个跨膜结构域分为N端一侧的一个大的细胞外结构域和C端一侧的一个小的细胞内结构域。细胞外结构域有一个富含半胱氨酸的区域，包含四个8个半胱氨酸基序的重复序列。在其他成熟β亚基的细胞外结构域中发现的所有56个半胱氨酸残基都存在于这个β亚基中。这里报道的β亚基与β3亚基有特别高的同源性。该分子的信使核糖核酸（mRNA）大小约为3.5千碱基对（kbp），在各种细胞类型中表达。其他研究人员最近报道了与玻连蛋白受体α亚基相关的其他β亚基。该分子推导的氨基酸序列包含这些β亚基之一βx的N端部分氨基酸序列。本文所述的β亚基似乎与βx亚基相同，并作为玻连蛋白受体的β亚基发挥作用。
