Comparison of the Functional Characteristics of the Nucleotide Binding Domains of Multidrug Resistance Protein 1

Abstract

Multidrug Resistance Protein 1 (MRP1) 1 is a member of the ATP-binding cassette (ABC) superfamily of transmembrane transporters that has been shown to confer resistance to a variety of natural product type drugs (1-6). The drug resistance phenotype conferred by MRP1 is similar to that resulting from overexpression of P-glycoprotein (P-gp) (reviewed in Refs. 7-9) and is typically associated with an ATP-dependent decrease in drug accumulation and an increase in drug efflux (4, 6). Although both ABC proteins can function as energy-dependent efflux pumps for a range of natural product type drugs, there is very limited primary structure similarity between them, and phylogenetic analyses suggest that they evolved from different ancestral proteins. There is also considerable evidence that the mechanisms by which MRP1 and P-gp transport drugs are different (reviewed in Ref. 8).In addition to its ability to confer multidrug resistance, MRP1, unlike P-gp, has been shown by in vitro studies using inside-out membrane vesicles to transport a structurally diverse array of organic, anionic conjugates (reviewed in Ref. 9). These include GSH-, glucuronide-, and sulfate-conjugated aliphatic, prostanoid, and heterocyclic compounds. The two highest affinity substrates identified to date are the proinflammatory cysteinyl leukotriene C 4 (LTC 4 ) (10 -12) and the GSH-

Identification of Proline Residues in the Core Cytoplasmic and Transmembrane Regions of Multidrug Resistance Protein 1 (MRP1/ABCC1) Important for Transport Function, Substrate Specificity, and Nucleotide Interactions

“…Thus, our present observations suggest that the CL7 Pro 1150 mutation somehow compromises the ability of NBD2 to hydrolyze ATP and/or trap ADP in the presence of vanadate and BeF. This could contribute, at least in part, to the moderately reduced ability of the P1150A mutant to transport LTC 4 , because previous studies have indicated that ATP binding/ hydrolysis at NBD2 plays a dominant role in the transport of this substrate (46,56). However, it is not immediately obvious how reduced ATP binding/hydrolysis activity at NBD2 can be reconciled with the enhanced ability of the P1150A mutant to transport E 2 17␤G and MTX.…”

“…-enriched membrane vesicle proteins were photolabeled with 8-azido-[␣-32 P]ATP essentially as described (46,47). Briefly, membrane vesicles (20 g) were dispersed in 20 l of transport buffer containing 5 mM MgCl 2 and 5 M 8-azido-[␣-32 P]ATP (1 Ci).…”

Structure and function of ABC transporters: the ATP switch provides flexible control

“…For some ABC transporters, the 'choice' of which NBD hydrolyses first may be stochastic [65]. For others, there is a clear asymmetry: for MRP1, NBD2 appears to hydrolyse ATP initially [66,74], and in CFTR, hydrolysis of one ATP is much slower than the other [84]. Nevertheless, the net result is the same: destabilisation of the 'closed dimer' albeit with different kinetic control.…”

ATP-sensitive K channel channel/enzyme multimer: Metabolic gating in the heart

“…Thus in contrast to certain ABC proteins NBD1 of SUR apparently does not hydrolyze ATP but possesses relatively stable nucleotide binding. Indeed, in the presence of Mg 2+ , NBD1 but not NBD2 of SUR could be labeled with 8-azido [γ-32 P]ATP suggesting that at least one hydrolytic cycle occurred at the second domain prior to labeling leaving the possibility only for tagging of NBD2 with of 8-azido-[α-32 P]ATP [44,45]. Asymmetrical properties of nucleotide interactions with NBDs correlate with the different structural homology between NBDs.…”

“…~40% sequence homology of SUR2A and CFTR NBD1s, as well as ~40% between the NBD2s of these two ABC proteins). In the SUR close relatives MRP1 and CFTR NBD2 also typically more catalytically active than NBD1 [44][45][46].…”