Analysis of the C-terminal domain of SccA, a putative cell wall stress receptor in

Abstract

Aspergillus nidulans is a filamentous fungus that has been used as a model organism for many eukaryotic processes. Its research implications are far-reaching because fungi have both negative and positive effects on many aspects in medicine, industry, and the environment. Studying the cell wall specifically is important as this structure is not present in animal cells and could potentially serve as a target for medical treatment in many threatening fungal infections. This research aims to elucidate the function of the novel gene designated SccA which affects cell wall integrity in A. nidulans. Plasmidbased, overexpression of SccA can suppress the calC2 mutation in protein kinase C (PkcA), which results in hypersensitivity to the chitin-binding agent Calcofluor White (CFW). It has previously been shown that hypersensitivity to CFW is indicative of cell wall integrity defects in both yeast and filamentous fungi. SccA is predicted to have a single transmembrane domain, an extracellular domain rich in serine and threonine amino acids, and a short cytoplasmic C-terminus of 59 amino acids. No sequence homologues exist in yeast, but structurally there is great similarity between SccA and other stress receptors. The C-terminal domains of yeast stress receptors like Wsc1 and Mid2 have been shown to play important roles in signal transduction upstream from Pkc. In an analysis of C-terminal truncation mutants, we have shown for the first time in A. nidulans that the C-terminal domain of SccA is also essential in proper cell wall integrity function.