ABCC1(人多药耐药蛋白1(hMRP1))是一种ATP结合盒转运蛋白,可流出异种和内源性有机阴离子,并通过主动药物流出赋予多药耐药性。hMRP1的17个跨膜α-螺旋分布在三个跨膜结构域(MSD0、1、2)中,其中MSD1、2各自随后是核苷酸结合结构域以形成4结构域核心结构。下降α-螺旋中MSD1的第一个细胞质环(CL4)中的八个保守残基(Gly392,Tyr404,Arg405),垂直耦合螺旋(Asn412,Arg415,Lys416),和上升的α-螺旋(Glu422,Phe434)被靶向用于诱变。具有丙氨酸和偶联螺旋残基的相同电荷取代的突变体在HEK细胞中以野生型hMRP1水平表达,并且它们的转运活性仅中度受损。相比之下,侧翼氨基酸的突变体(G392I,Y404A,R405A/K,E422A/D,和F434Y)表达非常差,尽管Y404F,E422D,和F434A容易表达和运输能力。建模分析表明Glu422和Arg615可以形成可能稳定转运蛋白表达的离子对。然而,不能提高hMRP1水平的交换突变E422R/R615E不支持这一点.需要伴随严格的生化验证的其他结构来更好地理解对于稳定的hMRP1表达至关重要的键合相互作用。
ABCC1 (human multidrug resistance protein 1 (hMRP1)) is an ATP-binding cassette transporter which effluxes xeno- and endobiotic organic anions and confers multidrug resistance through active drug efflux. The 17 transmembrane α-helices of hMRP1 are distributed among three membrane spanning domains (MSD0, 1, 2) with MSD1,2 each followed by a nucleotide binding domain to form the 4-domain core structure. Eight conserved residues in the first cytoplasmic loop (CL4) of MSD1 in the descending α-helix (Gly392, Tyr404, Arg405), the perpendicular coupling helix (Asn412, Arg415, Lys416), and the ascending α-helix (Glu422, Phe434) were targeted for mutagenesis. Mutants with both alanine and same charge substitutions of the coupling helix residues were expressed in HEK cells at wild-type hMRP1 levels and their transport activity was only moderately compromised. In contrast, mutants of the flanking amino acids (G392I, Y404A, R405A/K, E422A/D, and F434Y) were very poorly expressed although Y404F, E422D, and F434A were readily expressed and transport competent. Modeling analyses indicated that Glu422 and Arg615 could form an ion pair that might stabilize transporter expression. However, this was not supported by exchange mutations E422R/R615E which failed to improve hMRP1 levels. Additional structures accompanied by rigorous biochemical validations are needed to better understand the bonding interactions crucial for stable hMRP1 expression.