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Inactivation of the Podospora anserina vegetative incompatibility locus het-c, whose product resembles a glycolipid transfer protein, drastically impairs ascospore production.

ABSTRACT: The het-c locus contains different alleles that elicit nonallelic vegetative incompatibility through specific interactions with alleles of the unlinked loci het-e and het-d. The het-c2 allele has been cloned. It encodes a 208-amino acid polypeptide that is similar to a glycolipid transfer protein purified from pig brain. Disruption of this gene drastically impairs ascospore production in homozygous crosses, and some mutants exhibit abnormal branching of apical hyphae. The protein encoded by het-c2 is essential in the biology of the fungus and may be involved in cell-wall biosynthesis.

SUBMITTER: Saupe S

PROVIDER: S-EPMC44110 | biostudies-other | 1994 Jun

REPOSITORIES: biostudies-other

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Inactivation of the Podospora anserina vegetative incompatibility locus het-c, whose product resembles a glycolipid transfer protein, drastically impairs ascospore production.

Saupe S S Descamps C C Turcq B B Bégueret J J

Proceedings of the National Academy of Sciences of the United States of America 19940601 13

The het-c locus contains different alleles that elicit nonallelic vegetative incompatibility through specific interactions with alleles of the unlinked loci het-e and het-d. The het-c2 allele has been cloned. It encodes a 208-amino acid polypeptide that is similar to a glycolipid transfer protein purified from pig brain. Disruption of this gene drastically impairs ascospore production in homozygous crosses, and some mutants exhibit abnormal branching of apical hyphae. The protein encoded by het- ...[more]

PMID: 8016091

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Natural variation of heterokaryon incompatibility gene het-c in Podospora anserina reveals diversifying selection.

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The mechanism of toxicity in HET-S/HET-s prion incompatibility.

Project description:The HET-s protein from the filamentous fungus Podospora anserina is a prion involved in a cell death reaction termed heterokaryon incompatibility. This reaction is observed at the point of contact between two genetically distinct strains when one harbors a HET-s prion (in the form of amyloid aggregates) and the other expresses a soluble HET-S protein (96% identical to HET-s). How the HET-s prion interaction with HET-S brings about cell death remains unknown; however, it was recently shown that this interaction leads to a relocalization of HET-S from the cytoplasm to the cell periphery and that this change is associated with cell death. Here, we present detailed insights into this mechanism in which a non-toxic HET-s prion converts a soluble HET-S protein into an integral membrane protein that destabilizes membranes. We observed liposomal membrane defects of approximately 10 up to 60 nm in size in transmission electron microscopy images of freeze-fractured proteoliposomes that were formed in mixtures of HET-S and HET-s amyloids. In liposome leakage assays, HET-S has an innate ability to associate with and disrupt lipid membranes and that this activity is greatly enhanced when HET-S is exposed to HET-s amyloids. Solid-state nuclear magnetic resonance (NMR) analyses revealed that HET-s induces the prion-forming domain of HET-S to adopt the β-solenoid fold (previously observed in HET-s) and this change disrupts the globular HeLo domain. These data indicate that upon interaction with a HET-s prion, the HET-S HeLo domain partially unfolds, thereby exposing a previously buried ∼34-residue N-terminal transmembrane segment. The liberation of this segment targets HET-S to the membrane where it further oligomerizes, leading to a loss of membrane integrity. HET-S thus appears to display features that are reminiscent of pore-forming toxins.

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