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Hansenula polymorpha Pex1p and Pex6p are peroxisome‐associated AAA proteins that functionally and physically interact
Author(s) -
Kiel J. A. K. W.,
Hilbrands R. E.,
van der Klei I. J.,
Rasmussen S. W.,
Salomons F. A.,
van der Heide M.,
Faber K. N.,
Cregg J. M.,
Veenhuis M.
Publication year - 1999
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/(sici)1097-0061(199908)15:11<1059::aid-yea434>3.0.co;2-i
Subject(s) - peroxisome , biology , peroxisomal targeting signal , membrane protein , cytosol , cell fractionation , vesicle associated membrane protein 8 , microbiology and biotechnology , mutant , biochemistry , microbody , complementation , gene , membrane , enzyme
We have cloned the Hansenula polymorpha PEX1 and PEX6 genes by functional complementation of the corresponding peroxisome‐deficient ( pex ) mutants. The gene products, HpPex1p and HpPex6p, are ATPases which both belong to the AAA protein family. Cells deleted for either gene (Δ pex1 or Δ pex6 ) were characterized by the presence of small peroxisomal remnants which contained peroxisomal membrane proteins and minor amounts of matrix proteins. The bulk of the matrix proteins, however, resided in the cytosol. In cell fractionation studies HpPex1p and HpPex6p co‐sedimented with the peroxisomal membrane protein HpPex3p in both wild‐type cells and in Δ pex4 , Δ pex8 or Δ pex14 cells. Both proteins are loosely membrane‐bound and face the cytosol. Furthermore, HpPex1p and HpPex6p physically and functionally interact in vivo . Overexpression of PEX6 resulted in defects in peroxisomal matrix protein import. By contrast, overexpression of PEX1 was not detrimental to the cells. Interestingly, co‐overproduction of HpPex1p rescued the protein import defect caused by HpPex6p overproduction. Overproduced HpPex1p and HpPex6p remained predominantly membrane‐bound, but only partially co‐localized with the peroxisomal membrane protein HpPex3p. Our data indicate that HpPex1p and HpPex6p function in a protein complex associated with the peroxisomal membrane and that overproduced, mislocalized HpPex6p prevents HpPex1p from reaching its site of activity. Copyright © 1999 John Wiley & Sons, Ltd.