HUMAN ERYTHROCYTE DEMATIN AND PROTEIN-4.2 (PALLIDIN) ARE ATP BINDING-PROTEINS

Dematin and protein 4.2 are peripheral membrane proteins associated wi th the cytoplasmic surface of the human erythrocyte plasma membrane. I soforms of dematin and protein 4.2 exist in many nonerythroid cells. I n solution, dematin is a trimeric protein containing two subunits of 4 8 kDa and one subunit of 52 kDa. Recent determination of the primary s tructure of the 52 kDa subunit of dematin showed that it contains an a dditional 22-amino acid sequence in the headpiece domain. An alignment of the 22-amino acid insertion sequence revealed that the 52 kDa subu nit of dematin shares a novel 11-amino acid motif with protein 4.2. In this communication, we report that the conserved 11-amino acid motif in dematin(52) and protein 4.2 contains a nucleotide binding P-loop. D irect binding of ATP is demonstrated to the glutathione S-transferase fusion proteins containing corresponding segments of dematin(52) and p rotein 4.2 as well as to purified protein 4.2. The binding of ATP to t he recombinant domains of dematin(52) and protein 4.2 is specific, sat urable, and of high affinity. The nucleotide specificity of the P-loop is restricted to ATP since no detectable binding was observed with GT P. These results show that the 11-amino acid motif provides an ATP bin ding site in dematin(52) and protein 4.2. Although the functional sign ificance of ATP binding is not yet clear, our findings open new perspe ctives for the function of dematin and protein 4.2 in vivo.