Berk P D, Wada H, Horio Y, Potter B J, Sorrentino D, Zhou S L, Isola L M, Stump D, Kiang C L, Thung S
Department of Medicine (Hepatic Research Group), Mount Sinai School of Medicine, New York, NY 10029.
Proc Natl Acad Sci U S A. 1990 May;87(9):3484-8. doi: 10.1073/pnas.87.9.3484.
The hepatic plasma membrane fatty acid-binding protein (h-FABPPM) and the mitochondrial isoenzyme of glutamic-oxaloacetic transaminase (mGOT) of rat liver have similar amino acid compositions and identical amino acid sequences for residues 3-24. Both proteins migrate with an apparent molecular mass of 43 kDa on SDS/polyacrylamide gel electrophoresis, have a similar pattern of basic charge isomers on isoelectric focusing, are eluted similarly from four different high-performance liquid chromatographic columns, have absorption maxima at 435 nm under acid conditions and 354 nm at pH 8.3, and bind oleate with a Ka approximately 1.2-1.4 x 10(7) M-1. Sinusoidally enriched liver plasma membranes and purified h-FABPPM have GOT enzymatic activity; the relative specific activities (units/mg) of the membranes and purified protein suggest that h-FABPPM constitutes 1-2% of plasma membrane protein in the rat hepatocyte. Monospecific rabbit antiserum against h-FABPPM reacts on Western blotting with mGOT, and vice versa. Antisera against both proteins produce plasma membrane immunofluorescence in rat hepatocytes and selectively inhibit the hepatocellular uptake of [3H]oleate but not that of [35S]sulfobromophthalein or [14C]taurocholate. The inhibition of oleate uptake produced by anti-h-FABPPM can be eliminated by preincubation of the antiserum with mGOT; similarly, the plasma membrane immunofluorescence produced by either antiserum can be eliminated by preincubation with the other antigen. These data suggest that h-FABPPM and mGOT are closely related.
大鼠肝脏的肝质膜脂肪酸结合蛋白（h - FABPPM）和谷氨酸草酰乙酸转氨酶的线粒体同工酶（mGOT）具有相似的氨基酸组成，并且在第3至24位残基上具有相同的氨基酸序列。在SDS/聚丙烯酰胺凝胶电泳上，这两种蛋白质的表观分子量均为43 kDa，在等电聚焦时有相似的碱性电荷异构体模式，从四种不同的高效液相色谱柱上的洗脱方式相似，在酸性条件下的最大吸收波长为435 nm，在pH 8.3时为354 nm，并且以约1.2 - 1.4×10⁷ M⁻¹的Ka结合油酸。富含窦状隙的肝质膜和纯化的h - FABPPM具有GOT酶活性；膜和纯化蛋白的相对比活性（单位/毫克）表明，h - FABPPM占大鼠肝细胞质膜蛋白的1 - 2%。针对h - FABPPM的单特异性兔抗血清在蛋白质印迹上与mGOT发生反应，反之亦然。针对这两种蛋白质的抗血清在大鼠肝细胞中产生质膜免疫荧光，并选择性抑制[³H]油酸的肝细胞摄取，但不抑制[³⁵S]磺溴酞钠或[¹⁴C]牛磺胆酸盐的摄取。抗h - FABPPM产生的油酸摄取抑制可通过抗血清与mGOT预孵育来消除；同样，任一抗血清产生的质膜免疫荧光可通过与另一种抗原预孵育来消除。这些数据表明h - FABPPM和mGOT密切相关。
