Study of the nucleotide-binding domain 1 of the human transporter protein MRP6

Multidrug-resistance-associated protein 6 (mrp6/abcc6) is a protein belonging to the abc transporter family. proteins in this family share many characteristic structural features,including two membrane-spanning domains and two nucleotide-binding domains (nbd1 and nbd2),that function cooperatively but not equally bind and hydrolyze atp. the mrp6 protein is structurally and functionally poorly characterized. previously,we showed,by nmr spectroscopy,that a fragment of mrp6-nbd1 presents helical structure and fluorescence experiments demonstrated that peptide binds atp. these data suggested that the study on selected regions could be a valid approach to define the structure of mrp6. in the present study,to better characterize mrp6-nbd1,we report data of cd spectroscopy,nucleotide binding and atp hydrolysis on two different polypeptides,one corresponding to the full-length nbd1 domain (residues from asp-627 to leu-851) and the other is a shorter polypeptide (residues from arg-648 to thr-805) without some key residues. we report that both polypeptides are highly structured in aqueous buffer and in 20% trifluoroethanol showing considerable helical and (3-structure content. the atp hydrolysis activity is exhibited only by the full-length nbd1 domain. comparison between our findings and the structurally well characterized mrp1-nbd1 supports the role of h-loop for the atp hydrolysis and of a-loop in stabilizing the atp binding. © 2010 bentham science publishers ltd.