Chen D, Guo J, Miki T, Tachibana M, Gahl W A
Section on Human Biochemical Genetics, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA.
Biochem Mol Med. 1997 Feb;60(1):27-37. doi: 10.1006/bmme.1996.2559.
Rabs are prenylated, membrane-bound proteins involved in vesicular fusion and trafficking. We isolated the complete cDNAs of two rab isoforms, rab27a and rab27b, from human melanoma cells and melanocytes, Rab27a is the human homolog of a rat megakaryocyte rab called ram p25. Rab27b corresponds to a small GTP-binding protein, c25KG, which was previously purified from platelets but whose cDNA had not been cloned. Sequence comparisons with known rabs indicate that rab27a and rab27b comprise a melanocyte/platelet subfamily within the rab family. In addition, rab27a was expressed in a large variety of cell and tissue types, excluding brain, and rab27b manifested itself primarily in testis. Bacterially expressed and purified rab27a and rab27b exhibited GTP-binding activity and can now be used for antibody production and studies of the substrate specificities of geranylgeranyl transferase. In addition, the expression of rab27a and rab27b in both melanocytes and platelets makes them candidates for involvement in mouse and human disorders characterized by the combination of pigment dilution and a platelet storage pool defect.
Rabs是参与囊泡融合和运输的异戊二烯化的膜结合蛋白。我们从人黑素瘤细胞和黑素细胞中分离出两种rab亚型（rab27a和rab27b）的完整cDNA。Rab27a是一种名为ramp25的大鼠巨核细胞rab的人类同源物。Rab27b对应于一种小GTP结合蛋白c25KG，该蛋白先前已从血小板中纯化出来，但其cDNA尚未克隆。与已知Rabs的序列比较表明，rab27a和rab27b在rab家族中构成一个黑素细胞/血小板亚家族。此外，rab27a在除脑以外的多种细胞和组织类型中表达，而rab27b主要在睾丸中表达。细菌表达并纯化的rab27a和rab27b表现出GTP结合活性，现在可用于抗体生产以及香叶基香叶基转移酶底物特异性的研究。此外，rab27a和rab27b在黑素细胞和血小板中的表达使它们成为参与以色素稀释和血小板储存池缺陷为特征的小鼠和人类疾病的候选因素。
