A LOW-TEMPERATURE-RESPONSIVE GENE FROM BARLEY ENCODES A PROTEIN WITH SINGLE-STRANDED NUCLEIC ACID-BINDING ACTIVITY WHICH IS PHOSPHORYLATED IN-VITRO

A low-temperature-responsive gene, bit 801, isolated from a winter bar ley (Hordeum vulgare L.) cDNA library prepared from leaf meristematic tissue, was sequenced. The deduced amino acid sequence predicts a glyc ine-rich RNA-binding protein (GR-RNP) which was homology to stress-res ponsive GR-RNPs from several other plant species. BLT 801 is a two-dom ain protein, the amino-terminal domain comprises a consensus RNA-bindi ng domain similar to that found in many eukaryotic genes and the carbo xy-terminal domain is extremely glycine-rich (68.5% glycine). Bit 801 mRNA also accumulates in response to the phytohormone abscisic acid. T he protein encoded by bit 801 has been produced as a recombinant fusio n protein using a bacterial expression vector. The fusion protein, a c himaera of glutathione S-transferase and BLT 801, has been used in stu dies to determine nucleic acid binding and other characteristics. Bind ing studies with single-stranded nucleic acids show that BLT 801 has a ffinity for homoribopolymers G, A and U but not C, it also binds to si ngle-stranded DNA and selects RNA molecules containing open loop struc tures enriched in adenine but low in cytosine. BLT 801 has a consensus motif for phosphorylation by cAMP protein kinase (PKA) at the junctio n between the two domains which can be phosphorylated by PKA in vitro and which, by analogy to animal studies, may have significance for con trolling enzyme function.