Isoprenylation of the plant molecular chaperone ANJ1 facilitates membrane association and function at high temperature.
We demonstrate that ANJ1, a higher plant homolog of the bacterial molecular chaperone DnaJ, is a substrate in vitro for protein farnesyl- and geranylgeranyl-transferase activities present in cell extracts of the plant Atriplex nummularia and yeast Saccharomyces cerevisiae. Isoprenylation did not occur when cysteine was replaced by serine in the CAQQ motif at the carboxyl terminus of ANJ1, indicating that this sequence functions as a CaaX consensus sequence for polyisoprenylation (where C is cysteine, a is an aliphatic residue, and X is any amino acid residue). Substitution of leucine for the terminal glutamine did not result in the expected geranylgeranylation as occurs with mammalian proteins containing a carboxyl-terminal leucine. Unlike the wild-type ANJ1, neither of the proteins containing these amino acid substitutions could functionally complement the yeast temperature-sensitive mutant mas5. Farnesylation enhanced the association of ANJ1 with A. nummularia microsomal membranes. Electrophoretic mobility of ANJ1 from the plant indicated that the protein is isoprenylated in vivo.
Center for Plant Environmental Stress Physiology, Purdue University, West Lafayette, IN 47907-1165.
J K
JK
Zhu
R A
RA
Bressan
P M
PM
Hasegawa
D019883:Alkyl and Aryl Transferases; D000595:Amino Acid Sequence; D001483:Base Sequence; D004926:Escherichia coli / Q000235:genetics; D051231:Farnesyltranstransferase; D005816:Genetic Complementation Test; D008715:Methionine / Q000378:metabolism; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D016366:Open Reading Frames; D018521:Plant Physiological Phenomena; D010940:Plant Proteins / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism*; D010944:Plants / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D017368:Protein Prenylation; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D013379:Substrate Specificity; D014166:Transferases / Q000378:metabolism
C083280:ANJ1 protein, Atriplex nummularia; D009838:Oligodeoxyribonucleotides; D010940:Plant Proteins; D011994:Recombinant Proteins; D008715:Methionine; D014166:Transferases; D019883:Alkyl and Aryl Transferases; C083291:geranylgeranyltransferase type-I; D051231:Farnesyltranstransferase