MRPs come in two types of structures: the MRP1 type, shared by MRP2, 3, 6 and 7; and the MRP4 type, shared by MRP5. This chapter focuses on MRP3–7. The MRP1 type has an additional NH2- terminal domain, which is thought to have five transmembrane segments and is not present in the MRP4 type. In MRP1, this domain is dispensable for transport function, explaining why proteins that differ substantially in size and putative structure, like MRP1 and MRP4, can still have similar functions. Human MRP3, also known as MOAT-D or cMOAT-2, and formally designated ABCC3 was first spotted by Allikmets and co-workers in their initial inventory of the human ABC superfamily. The first substrates of MRP4 were deduced with the human T-lymphoid cell line CEM-r1. All MRPs studied thus far are organic anion pumps, but they differ widely in their preferred substrate or tissue location.
|Title of host publication||ABC Proteins From Bacteria to Man|
|Editors||I. Barry Holland, Susan P. Cole, Karl Kuchler, Christopher F. Higgins|
|Publication status||Published - 2002|