COMPLETE AMINO-ACID-SEQUENCE OF PUROINDOLINE, A NEW BASIC AND CYSTINE-RICH PROTEIN WITH A UNIQUE TRYPTOPHAN-RICH DOMAIN, ISOLATED FROM WHEAT ENDOSPERM BY TRITON X-114 PHASE PARTITIONING

A new basic protein has been isolated from wheat endosperm by Triton X -1 14 phase partitioning. It contains five disulfide bridges and is co mposed of equal amounts of a polypeptide chain of 115 amino acid resid ues and of the same chain with a C-terminus dipeptide extension. The m ost striking sequence feature is the presence of a unique tryptophan-r ich domain so that this protein isolated from wheat seeds has been nam ed puroindoline. The similar phase partitioning behavior in Triton X-1 14 of this basic cystine-rich protein and of purothionins suggests th at puroindoline may also be a membranotoxin that might play a role in the defense mechanism of plants against microbial pathogens.