A transcript encoding a nucleic acid-binding protein specifically expressed in maize seeds

A cDNA clone has been obtained for a low-abundance, seed-specific mRNA that encodes a polypeptide which defines a novel family of plant proteins with some similarities to the DnaJ class of molecular chaperones. The MEM1 (Maiz e Endosperm Motif binding protein) protein is capable of binding to the end osperm motif and activating transcription in the yeast one-hybrid system. R ecombinant MEM1 was shown to bind in vitro to nucleic acids, with a prefere nce for RNA over DNA. MEM1 is capable of forming homodimers, a property tha t is dependent on a domain close to the C-terminus of the protein. The prot ein is expressed in mid- to late-term endosperm cells. Subcellular fraction ation and size fractionation under non-denaturing conditions indicate that the protein is present in the cytosol of endosperm cells. Possible roles of MEM1 in endosperm and protein body development are discussed.