The primary and subunit structure of a novel type killer toxin produced by a halotolerant yeast, Pichia farinosa

• Published in: The Journal of biological chemistry 1994-01, Vol.269 (4), p.3041-3046
• Main Authors: Suzuki, C, Nikkuni, S
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Analytical, structural and metabolic biochemistry; Base Sequence; Biological and medical sciences; Carboxypeptidases - metabolism; Chromatography, Ion Exchange; DNA Primers; DNA, Fungal - chemistry; DNA, Fungal - metabolism; Electrophoresis, Polyacrylamide Gel; FITOTOXICIDAD; Fundamental and applied biological sciences. Psychology; GENE; GENES; Genes, Fungal; Killer Factors, Yeast; Macromolecular Substances; MICOTOXINAS; Miscellaneous; Molecular Sequence Data; Molecular Weight; MYCOTOXINE; Mycotoxins - biosynthesis; Mycotoxins - chemistry; Mycotoxins - isolation & purification; PEPTIDE; Peptide Fragments - chemistry; Peptide Fragments - isolation & purification; PEPTIDOS; PHYTOTOXICITE; PICHIA; Pichia - genetics; Pichia - metabolism; Pichia farinosa; Polymerase Chain Reaction; Proprotein Convertases; Protein Precursors - biosynthesis; Protein Precursors - chemistry; Protein Processing, Post-Translational; Protein Sorting Signals - chemistry; Proteins; Restriction Mapping; Saccharomyces cerevisiae - metabolism; Saccharomyces cerevisiae Proteins; SALINIDAD; SALINITE; SECUENCIA NUCLEICA; SEQUENCE NUCLEIQUE; Subtilisins - metabolism; TOLERANCE AU SEL; TOLERANCIA A LA SAL
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/s0021-9258(17)42044-8

A halotolerant yeast, Pichia farinosa KK1 strain, produces a unique killer toxin termed SMK toxin (salt-mediated killer toxin) which shows its maximum killer activity in the presence of 2 M NaCl. The toxin consists of two distinct subunits, alpha and beta, which are tightly linked without a disulfide bond under acidic conditions, even in the presence of 6 M urea. Under neutral conditions, however, the a subunit precipitates, resulting in the dissociation of the subunits and the loss of killer activity. The nucleotide sequence of the SMK1 gene predicts a 222 amino acid preprotoxin with a typical signal sequence, the hydrophobic alpha, an interstitial gamma polypeptide with a putative glycosylation site, and the hydrophilic beta. Amino acid sequence analyses of peptide fragments including the carboxyl-terminal peptides from each subunit suggest that the alpha and beta subunits consist of amino acid residues 19-81 and 146-222 of the preprotoxin, respectively, and the molecular weight of the mature alpha-beta dimer is 14,214. The KEX2-like endopeptidase and KEX1-like carboxypeptidase may be involved in the stepwise processing of the SMK preprotoxin. The maturation process and the functions of the SMK toxin are compared with the K1 toxin of Saccharomyces cerevisiae