Isolation, molecular characterization, and tissue-specific expression of ECP-51 and ECP-54 (TIP49), two homologous, interacting erythroid cytosolic proteins

We isolated two proteins, ECP-51 and ECP-54, from human erythrocyte cytosol by affinity chromatography using a peptide of the integral membrane protei n stomatin as bait. Partial amino acid sequence information obtained by mic rosequencing allowed us to clone the respective cDNAs. Analysis of the nucl eotide sequences revealed that ECP-51 and ECP-54 are homologous (44.2% amin o acid identity) and contain ATP-binding sites. ECP-54 was identified as TI P49/RUVBL1/NMP238, which is a component of a large nuclear protein complex, possibly the RNA polymerase II holoenzyme; ECP-51 is a novel protein. Usin g the two-hybrid system, we showed that these proteins interact with each o ther. The interaction of ECP-51 and ECP-54 with the stomatin peptide and th e localization to the nucleus and cytoplasm suggest an additional function for these proteins as chaperone components. (C) 1999 Elsevier Science B.V. All rights reserved.