Structure and heterologous expression of the Ustilago maydis viral toxin KP4.
Killer toxins are polypeptides secreted by some fungal species that kill sensitive cells of the same or related species. In the best-characterized cases, they function by creating new pores in the cell membrane and disrupting ion fluxes. Immunity or resistance to the toxins is conferred by the preprotoxins (or products thereof) or by nuclear resistance genes. In several cases, the toxins are encoded by one or more genomic segments of resident double-stranded RNA viruses. The known toxins are composed of one to three polypeptides, usually present as multimers. We have further characterized the KP4 killer toxin from the maize smut fungus Ustilago maydis. This toxin is also encoded by a single viral double-stranded RNA but differs from other known killer toxins in several respects: it has no N-linked glycosylation either in the precursor or in the mature polypeptide, it is the first killer toxin demonstrated to be a single polypeptide, and it is not processed by any of the known secretory proteinases (other than the signal peptidase). It is efficiently expressed in a heterologous fungal system.
Park
C M
CM
Department of Biological Sciences, State University of New York at Buffalo 14260.
Bruenn
J A
JA
Ganesa
C
C
Flurkey
W F
WF
Bozarth
R F
RF
Koltin
Y
Y
D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D018076:DNA, Complementary; D005656:Fungal Proteins / Q000737:chemistry* / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D013058:Mass Spectrometry / Q000379:methods; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009183:Mycotoxins / Q000737:chemistry* / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D010641:Phenotype; D043484:Proprotein Convertases; D011498:Protein Precursors / Q000737:chemistry* / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D011499:Protein Processing, Post-Translational / Q000502:physiology; D012330:RNA, Double-Stranded / Q000235:genetics / Q000302:isolation & purification; D012367:RNA, Viral / Q000235:genetics / Q000302:isolation & purification; D012441:Saccharomyces cerevisiae / Q000201:enzymology; D029701:Saccharomyces cerevisiae Proteins; D017421:Sequence Analysis; D013381:Subtilisins / Q000378:metabolism; D014170:Transformation, Genetic; D014588:Ustilago / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D014764:Viral Proteins
D018076:DNA, Complementary; D005656:Fungal Proteins; C086593:M2A protein, Ustilago maydis P4 virus; D009183:Mycotoxins; D011498:Protein Precursors; D012330:RNA, Double-Stranded; D012367:RNA, Viral; D029701:Saccharomyces cerevisiae Proteins; D014764:Viral Proteins; C086592:Ustilago maydis viral toxin KP4; D043484:Proprotein Convertases; D013381:Subtilisins; C058751:KEX2 protein, S cerevisiae