ABCB1 p.Tyr444*
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[hide] The Transmission Interfaces Contribute Asymmetrica... J Biol Chem. 2015 Jul 3;290(27):16954-63. doi: 10.1074/jbc.M115.652602. Epub 2015 May 18. Loo TW, Clarke DM
The Transmission Interfaces Contribute Asymmetrically to the Assembly and Activity of Human P-glycoprotein.
J Biol Chem. 2015 Jul 3;290(27):16954-63. doi: 10.1074/jbc.M115.652602. Epub 2015 May 18., [PMID:25987565]
Abstract [show]
P-glycoprotein (P-gp; ABCB1) is an ABC drug pump that protects us from toxic compounds. It is clinically important because it confers multidrug resistance. The homologous halves of P-gp each contain a transmembrane (TM) domain (TMD) with 6 TM segments followed by a nucleotide-binding domain (NBD). The drug- and ATP-binding sites reside at the interface between the TMDs and NBDs, respectively. Each NBD is connected to the TMDs by a transmission interface involving a pair of intracellular loops (ICLs) that form ball-and-socket joints. P-gp is different from CFTR (ABCC7) in that deleting NBD2 causes misprocessing of only P-gp. Therefore, NBD2 might be critical for stabilizing ICLs 2 and 3 that form a tetrahelix bundle at the NBD2 interface. Here we report that the NBD1 and NBD2 transmission interfaces in P-gp are asymmetric. Point mutations to 25 of 60 ICL2/ICL3 residues at the NBD2 transmission interface severely reduced P-gp assembly while changes to the equivalent residues in ICL1/ICL4 at the NBD1 interface had little effect. The hydrophobic nature at the transmission interfaces was also different. Mutation of Phe-1086 or Tyr-1087 to arginine at the NBD2 socket blocked activity or assembly while the equivalent mutations at the NBD1 socket had only modest effects. The results suggest that the NBD transmission interfaces are asymmetric. In contrast to the ICL2/3-NBD2 interface, the ICL1/4-NBD1 transmission interface is more hydrophilic and insensitive to mutations. Therefore the ICL2/3-NBD2 transmission interface forms a precise hydrophobic connection that acts as a linchpin for assembly and trafficking of P-gp.
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No. Sentence Comment
195 A52-tagged mutants Y444X were constructed so that tyrosine was replaced with a small (Ala), hydrophobic (Phe, Leu) or charged(Arg,Glu)residue.Forcomparison,thepreviouslycon- structed Y1087A, Y1087F, and Y1087L mutants were included (38) and additional mutants Y1087R and Y1087E were also constructed.
X
ABCB1 p.Tyr444* 25987565:195:19
status: NEW199 All the Y444X mutants except Y444E differed from their Tyr-1087 counterparts as they yielded detectable levels of mature 170 kDa P-gp.
X
ABCB1 p.Tyr444* 25987565:199:8
status: NEW205 The activity of Y1087 was almost completely inhibited when it was mutated to A, L, R, or E. In contrast, the Y444X mutations had less severe effects.
X
ABCB1 p.Tyr444* 25987565:205:109
status: NEW