Localization and post-translational processing of the wound-induced leucine aminopeptidase proteins of tomato.
Leucine aminopeptidase (LAP) is induced by wounding and bacterial pathogen infection in tomato. DNA blot analysis of XbaI-digested lambdalap genomic clones demonstrated that LapA1 and LapA2 cDNAs were encoded by two different LapA genes in the tomato genome. The coding and untranslated regions of LapA1 and LapA2 mRNAs shared more than 93% identity. The deduced amino acid sequences of LapA cDNA clones and in vitro translation of LapA1 mRNA indicated that LAP-A was synthesized as a 60-kDa precursor protein. The processing of a 60-kDa preLAP-A into the mature 55-kDa LAP-A was demonstrated in vivo by expression of the full-length LapA1 cDNA in insect cells. Sequencing of a single LAP-A form isolated from a two-dimensional polyacrylamide gel indicated that LAP-A proteins had two different N termini that were separated by two residues. The LAP-A presequence had features similar to chloroplast transit peptides. Comparison of LAP-A levels in chloroplast and total protein extracts from methyl jasmonate-treated leaves indicated that a small proportion of the LAP-A proteins was detected in the plastids. Inspection of the LAP-A presequence indicated the presence of a dibasic protease (Kex2/furin) processing site motif 6-8 residues upstream from the LAP-A N termini. Its potential role in LAP-A precursor biogenesis is discussed.
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Department of Botany and Plant Sciences and Graduate Genetics Group, University of California, Riverside, California 92521-0124, USA.
Chao
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Walling
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D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D018076:DNA, Complementary / Q000737:chemistry; D018744:DNA, Plant / Q000737:chemistry; D015252:Deoxyribonucleases, Type II Site-Specific / Q000378:metabolism; D015180:Electrophoresis, Gel, Two-Dimensional; D004790:Enzyme Induction; D007313:Insecta; D007931:Leucyl Aminopeptidase / Q000096:biosynthesis* / Q000235:genetics; D018551:Solanum lycopersicum; D008969:Molecular Sequence Data; D010935:Plant Diseases; D014176:Protein Biosynthesis; D011499:Protein Processing, Post-Translational
D018076:DNA, Complementary; D018744:DNA, Plant; C025580:endodeoxyribonuclease XBAI; D015252:Deoxyribonucleases, Type II Site-Specific; D007931:Leucyl Aminopeptidase