A putative precursor protein in the evolution of the bean α-amylase inhibitor

• Published in: Phytochemistry (Oxford) Vol. 43; no. 1; pp. 57 - 62
• Main Authors: Finardi-Filho, Flavio, Mirkov, T.Erik, Chrispeels, Maarten J.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Ltd 01.09.1996; Elsevier
• Subjects: alpha-Amylases - antagonists & inhibitors; Amino Acid Sequence; Analytical, structural and metabolic biochemistry; Biological and medical sciences; Chromosome Mapping; DNA, Complementary; Enzymes and enzyme inhibitors; Fabaceae - chemistry; Fabaceae - genetics; Fundamental and applied biological sciences. Psychology; Glycoproteins - chemistry; Glycoproteins - genetics; Hydrolases; Molecular Sequence Data; Plant Proteins - chemistry; Plant Proteins - genetics; Plants, Medicinal; Protein Precursors - chemistry; Sequence Homology, Amino Acid; Trypsin Inhibitors; arcelin; α-amylase inhibitor; phytohaemagglutinin; common bean; Leguminosae; Phaseolus vulgaris; Storage protein; Enzyme; Biological evolution; Enzyme inhibitor; Homology; Phytohemagglutinin; Gene expression; Grain legume; Dicotyledones; Glycosidases; Angiospermae; Hydrolases; Spermatophyta; α-Amylase; Locus; O-Glycosidases; Aminoacid sequence
• ISSN: 0031-9422; 1873-3700
• DOI: 10.1016/0031-9422(96)00184-7

Seeds of the common bean Phaseolus vulgaris and the tepary bean ( P. acutifolius) contain a family of plant defence proteins that includes phytohaemagglutinin (PHA), arcelin and α-amylase inhibitor (αAI). These homologous proteins differ by the absence of short loops at the surface of the protein and by the presence of a proteolytic processing site (Asn 77) that allows αAI to be post-translationally cleaved and activated. We now report the derived amino acid sequence of two amylase inhibitor-like (AIL) proteins that are not proteolytically processed, although they have the typical processing site. One protein is from the common bean, and the other from the tepary bean. On a dendrogram, these proteins are grouped with αAIs rather than with the arcelins or lectins. αAI differs from AIL primarily by the deletion of a 15-amino-acid segment from the middle of the AIL sequence. When αAI is expressed in tobacco, it is proteolytically processed to form an active molecule. However, AIL sequences are not processed. We suggest that the AIL proteins may be an intermediate in the evolution of an active αAI.