title: Nucleotide triphosphatase activity of the N-terminal nucleotide-binding domains of the multidrug resistance proteins P-glycoprotein and MRP1.
abstract: The multidrug resistance proteins P-glycoprotein (Pgp) and MRP1 are drug-efflux pumps. In this study, we compared the nucleotide triphosphatase activities of the isolated N-terminal nucleotide binding domains (NBD1) of Pgp and MRP1, and explored the potential role of the phosphorylation target domain of Pgp on the regulation of Pgp NBD1 ATPase activity. We found that: (1) the NBD1s of Pgp and MRP1 have ATPase and GTPase activities, (2) the K(m)s of Pgp NBD1 for ATP and GTP hydrolysis are identical, while the K(m) of MRP1 NBD1 for ATP is lower than that for GTP, and (3) phosphorylation of MLD by PKA or PKC produces a marginal increase of V(max) for ATP hydrolysis, without affecting the affinity for ATP. These results show efficient GTP hydrolysis by the NBD1s of Pgp and MRP1, and a minor role of phosphorylation in the control of Pgp NBD1 ATPase activity.
authors.affiliation: Membrane Protein Laboratory, Department of Physiology and Biophysics, The University of Texas Medical Branch Galveston, 301 University Boulevard, Galveston, TX 77555-0437, USA.
authors.forename: Denise M
authors.initials: DM
authors.lastname: Wilkes
authors.forename: Changsen
authors.initials: C
authors.lastname: Wang
authors.forename: Patricia C
authors.initials: PC
authors.lastname: Aristimuño
authors.forename: Ariel F
authors.initials: AF
authors.lastname: Castro
authors.forename: Guillermo A
authors.initials: GA
authors.lastname: Altenberg
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D018432:Drug Resistance, Multiple; D006160:Guanosine Triphosphate / Q000378:metabolism; D006801:Humans; D058619:Maltose-Binding Proteins; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000302:isolation & purification / Q000378:metabolism
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000251:Adenosine Triphosphatases; D000255:Adenosine Triphosphate; D002352:Carrier Proteins; D017868:Cyclic AMP-Dependent Protein Kinases; D006160:Guanosine Triphosphate; D058619:Maltose-Binding Proteins; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D011493:Protein Kinase C; D011993:Recombinant Fusion Proteins; C421109:multidrug resistance-associated protein 1