protein 蛋白质 tetraspanin 四跨膜蛋白 A protein with four transmembrane domains, small intracellular amino- and carboxyl-terminal regions, and two extracellular loops, a small one (EC1) and a larger one (EC2) of about 100 residues. The EC2 loop contains at least 4 cysteine residues, including a highly conserved 'CCG' motif. 具有四个跨膜结构域，细胞内氨基和羧基端小区域，以及两个细胞外环，一个小的（EC1）和一个大的（EC2）约100个残基的蛋白质。 EC2环含有至少4个半胱氨酸残基，包括高度保守的“CCG”基序。