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V Haucke

Publications and source records attributed to V Haucke.

23 records · Page 2Linked to original sources
PubMed1996

The Mas20p and Mas70p subunits of the protein import receptor of yeast mitochondria interact via the tetratricopeptide repeat motif in Mas20p: evidence for a single hetero-oligomeric receptor.

Protein import into yeast mitochondria is mediated by four integral outer membrane proteins which function as import receptors. These proteins (termed Mas20p, Mas22p, Mas37p and Mas70p) appear to exist as two subcomplexes: a Mas37p-Mas70p heterodimer and a less well characterized Mas20p-Mas22p complex. The subcomplexes interact functionally during protein import, but it has remained uncertain whether they are in direct contact with each other in vivo. Here we show that Mas20p and Mas70p can be cross-linked in intact mitochondria, or co-immunoprecipitated from digitonin-solubilized mitochondria. Furthermore, the cytosolic domains of these two proteins interact in the 'two-hybrid' system. Association of Mas20p and Mas70p is virtually abolished by a mutation in the single tetratricopeptide motif in Mas20p. This mutation specifically inhibits import of precursors that are first recognized by Mas37p-Mas70p and only then transferred to Mas20p-Mas22p. We conclude that the two receptor subcomplexes of the mitochondrial protein import receptor interact in vivo via their Mas20p and Mas70p subunits and that this interaction is functionally important.

Base Sequence↗
PubMed1995

The yeast mitochondrial protein import receptor Mas20p binds precursor proteins through electrostatic interaction with the positively charged presequence.

Protein import into yeast mitochondria is mediated by the four outer membrane receptors Mas70p, Mas37p, Mas20p, and Mas22p. These receptors may function as two subcomplexes: a Mas37p/Mas70p heterodimer and an acidic complex consisting of Mas20p and Mas22p. To assess the relative contribution of these subcomplexes to precursor binding, we allowed different precursors to bind to the surface of deenergized mitochondria, then reenergized the mitochondria and measured the chase of the bound precursors into the organelles. Productive binding of several precursors with a positively charged amino-terminal matrix targeting sequence, such as SU9-DHFR, hsp60, and mitochondrial cpn10, was strongly inhibited by salt, by low concentrations of a mitochondrial presequence peptide, and by a deletion of Mas20p, but was independent of Mas37p/Mas70p. In contrast, productive binding of the ADP/ATP carrier was not inhibited by salt, the presequence peptide, or a deletion of Mas20p, but was strongly dependent on Mas37p/Mas70p. The precursors of alcohol dehydrogenase III and the Rieske iron-sulfur protein had binding properties between these two extremes. The productively bound precursor of cpn10 could be cross-linked to Mas20p. We conclude that Mas20p binds mitochondrial precursor proteins through electrostatic interactions with the positively charged presequence, whereas Mas37p/Mas70p may recognize some feature(s) of the mature part of precursor proteins.

Amino Acid Sequence↗
PubMed1995

Mas37p, a novel receptor subunit for protein import into mitochondria.

By screening a collection of Saccharomyces cerevisiae mutants temperature sensitive for growth on a nonfermentable carbon source, we have isolated a gene (termed MAS37) which encodes a novel receptor for protein import into mitochondria. Mas37p is a 37-kD outer membrane protein with two putative membrane-spanning regions. Inactivation of the MAS37 gene renders cells temperature-sensitive for respiration-driven growth, inhibits import of precursors into isolated mitochondria, and is synthetically lethal with a deletion of one of the genes encoding the import receptors Mas70p or Mas20p. Inactivation of Mas37p with specific antibodies inhibits import of different precursors to different extents; the precursor specificity of Mas37p resembles that of the previously described import receptor Mas70p. Mas70p and Mas37p form a 1:1 complex in detergent extracts of mitochondria and overexpression of one protein enhances that of the other. We suggest that the Mas37p/Mas70p heterodimer functions as a receptor for protein import into yeast mitochondria and that the mitochondrial receptor system consists of hetero-oligomeric subcomplexes with distinct binding activities, but overlapping precursor specificities.

Amino Acid Sequence↗
PubMed1994

Incomplete arrest in the outer membrane sorts NADH-cytochrome b5 reductase to two different submitochondrial compartments.

The S. cerevisiae gene MCR1 encodes two mitochondrial isoforms of NADH-cytochrome b5 reductase. The primary translation product has an amino-terminal matrix-targeting signal, followed by a stretch of 21 uncharged amino acids. This precursor protein is inserted into the outer membrane, but only about one-third of the molecules become firmly anchored to the outer face of that membrane. The remaining molecules pass through the outer membrane into the inner membrane, are cleaved by inner membrane protease 1, and are released into the intermembrane space. Incomplete translocation arrest in the outer membrane is a novel mechanism by which the product of a single gene is sorted into different compartments of the same organelle.

Amino Acid Sequence↗