Structure and function of a fungal viral toxin KP4
Abstract
KP4 is a virally encoded fungal toxin expressed by the P4 killer fungal strain of Ustilago maydis. The virus coding this toxin, UMV P4, persistently infects the host and is symbiotic with the host by providing KP4 to kill competitive strains of the same fungi. KP4 has distinct physical properties compared to other fungal killer toxins, and likely a novel killing mechanism. The crystal structure of KP4 was determined to 1.75A resolution. KP4 belongs to the $\alpha/\beta$ sandwich family and has a unique topology comprised of a five stranded anti-parallel $\beta$-sheet with two anti-parallel $\alpha$-helices lying at ${\sim}45\sp\circ$ to these strands. Structural similarities between KP4 and scorpion toxins that target Na$\sp+$ channels on excitable membranes led to experiments showing that KP4 blocks both fungal and, unexpectedly, mammalian Ca$\sp{2+}$ channels. Albeit different in structural details, KP4 is similar to other channel inhibitors (i.e., scorpion toxins and $\omega$-toxins) in the shape and asymmetric surface charge distribution of the molecule. Therefore, KP4 could be a new tool for studying mammalian and fungal Ca$\sp{2+}$ channels, and these other Ca$\sp{2+}$ channel inhibitors may be useful lead compounds for new anti-fungal agents.
Degree
Ph.D.
Advisors
Smith, Purdue University.
Subject Area
Molecular biology|Botany|Biochemistry|Microbiology
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