Staff Members of the Institute of Biochemistry, TU Graz http://www ...

A
B
V
N
M
Figure 4: Electron microscopy of Pichia pastoris X33 wild type grown on glycerol (A).
Under these conditions mitochondria are well expressed. B: isolated mitochondria from
Pichia pastoris grown on glycerol. M, mitochondria; V, vacuole; N, nucleus; Bars. 0.5
and 2 µm. Pictures shown be curtsey of E. Ingolic, FELMI, TU Graz, Austria
Doctoral Thesis completed
Sabine Rosenberger
Phosphatidylethanolamine (PtdEtn) is an essential component in the yeast
Saccharomyces cerevisiae required for function and integrity of mitochondrial
membranes, for protein import/assembly into the inner mitochondrial membrane, for
GPI-anchor synthesis and vacuolar targeting. Biosynthesis of PtdEtn can be
accomplished by three different pathways, with the major route mediated by
phosphatidylserine decarboxylase 1 (Psd1p) residing in the inner mitochondrial
membrane (IMM). Deletion of PSD1 leads to a significant decrease of cellular and
mitochondrial PtdEtn thereby conferring a petite phenotype, which is characterized by
the loss of respiratory capacity and mitochondrial DNA. To identify a link between the
petite phenotype and disturbed lipid homeostasis in mitochondria a petite yeast strain
collection was screened for mutants with abnormal phospholipid patterns. This
approach unveiled some candidate genes, among them MRPL22. Deletion of MRPL22
leads to a decreased amount of cellular and mitochondrial PtdEtn similar to a psd1
deletion strain. Another major part of this thesis was focused on the assembly of PtdEtn
into peroxisomal membranes. To define the traffic routes of PtdEtn from their site of
synthesis to peroxisomes single and multiple mutants bearing defects in the different
pathways of PtdEtn synthesis were used. PtdEtn formed through all three pathways in
different subcellular membranes can be supplied to peroxisomes with comparable
efficiency.
International Cooperations
J. Cregg, Keck Graduate Institute of Applied Life Sciences, Claremont, CA, USA
I. Hapala, Slovak Academy of Sciences, Institute of Animal Biochemistry and Genetics,
Ivanka pri Dunaji, Slovak Republic
V. Tomekova, Department of Medical Chemistry, Biochemistry and Clinical
Biochemistry, Faculty of Medicine UPJS, Košice, Slovak Republic
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