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Saccharomyces cerevisiae cell wall chitin, the Kluyveromyces lactis zymocin receptor
Author(s) -
Jablonowski Daniel,
Fichtner Lars,
Martin Vera J.,
Klassen Roland,
Meinhardt Friedhelm,
Stark Michael J. R.,
Schaffrath Raffael
Publication year - 2001
Publication title -
yeast
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.923
H-Index - 102
eISSN - 1097-0061
pISSN - 0749-503X
DOI - 10.1002/yea.776
Subject(s) - chitin , saccharomyces cerevisiae , chitin synthase , biology , kluyveromyces lactis , yeast , biochemistry , cell wall , chitinase , microbiology and biotechnology , enzyme , chitosan
The exozymocin secreted by Kluyveromyces lactis causes sensitive yeast cells, including Saccharomyces cerevisiae , to arrest growth in the G 1 phase of the cell cycle. Despite its heterotrimeric (αβγ) structure, intracellular expression of its smallest subunit, the γ‐toxin, is alone responsible for the G 1 arrest. The α subunit, however, has a chitinase activity that is essential for holozymocin action from the cell exterior. Here we show that sensitive yeast cells can be rescued from zymocin treatment by exogenously applying crude chitin preparations, supporting the idea that chitin polymers can compete for binding to zymocin with chitin present on the surface of sensitive yeast cells. Consistent with this, holozymocin can be purified by way of affinity chromatography using an immobilized chitin matrix. PCR‐mediated deletions of ch itin s ynthesis ( CHS ) genes show that most, if not all, genetic scenarios that lead to complete loss ( chs3 Δ), blocked export ( chs7 Δ) or reduced activation ( chs4 Δ), combined with mislocalization ( chs4 Δ chs5 Δ; chs4 Δ chs6 Δ; chs4 Δ chs5 Δ chs6 Δ) of chitin synthase III activity (CSIII), render cells refractory to the inhibitory effects of exozymocin. In contrast, deletions in CHS1 and CHS2 , which code for CSI and CSII, respectively, have no effect on zymocin sensitivity. Thus, CSIII‐polymerized chitin, which amounts to almost 90% of the cell's chitin resources, appears to be the carbohydrate receptor required for the initial interaction of zymocin with sensitive cells. Copyright © 2001 John Wiley & Sons, Ltd.