Affiliation:
1. IACR-Long Ashton Research Station, Department of Agricultural Sciences, University of Bristol, Long Ashton, Bristol BS18 9AF, United Kingdom (J.H.A.B., S.P.S., P.R.S., N.G.H.)
Abstract
Abstract
A protein kinase was partially purified from barley (Hordeum vulgare L. cv Sundance) endosperm by ammonium sulfate fractionation, followed by ion-exchange, Reactive Blue, Mono-Q, and phosphocellulose chromatography. It was shown to phosphorylate Arabidopsis 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase and a synthetic peptide that was shown previously to act as a substrate for HMG-CoA reductase kinase purified from cauliflower, confirming it to be barley HMG-CoA reductase kinase. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the partially purified preparation showed the presence of a polypeptide with an approximate relative molecular weight (Mr) of 60,000, which is the size predicted for the barley sucrose nonfermenting-1 (SNF1)-related protein kinases BKIN2 and BKIN12. Antisera were raised to a rye (Secale cereale L.) SNF1-related protein kinase (RKIN1) expressed in Escherichia coli as a fusion with maltose-binding protein and to a synthetic peptide with a sequence that is conserved in, and specific to, plant members of the SNF1-related protein kinase family. The maltose-binding protein-RKIN1 fusion protein antiserum recognized a doublet of polypeptides with an approximate Mr of 60,000 in crude endosperm extracts and a single polypeptide in root extracts, which co-migrated with the smaller polypeptide in the endosperm doublet. Both antisera recognized a polypeptide with an approximate Mr of 60,000 in the partially purified protein kinase preparation, suggesting strongly that barley HMG-CoA reductase kinase is a member of the SNF1-related protein kinase family.
Publisher
Oxford University Press (OUP)
Subject
Plant Science,Genetics,Physiology