Investigation of the physiological and molecular functions of the mitochondrial carrier Sal1p.
Juraj Laco, Igor Zeman, Jordan Kolarov
Dept. of Biochemistry, Comenius University, Mlynska dolina CH-1, Bratislava, 84215, Slovakia
Transport of adenine nucleotides across the inner mitochondrial membrane is achieved by ADP/ATP carrier (AACp) encoded by three isoforms in S. cerevisiae. We have made previously for the first time triple aac1-3 deletion strain which was viable (Drgon, T. et al., 1991). As intramitochondrial ATP is essential for mitochondrial biogenesis and cell growth we suggested existence of an alternative transport mechanism of adenine nucleotides in the absence of AACp. Interestingly, disruption of the AAC2 gene was later found to be lethal in most other haploid laboratory strains. Recently a suppressor of aac2 lethality named SAL1 was identified (Chen, X. J., 2004). We have studied properties of strains with full-length, truncated or disrupted SAL1 gene. Cells incubated with specific inhibitor of AACp were able to grow only if they have full-length SAL1 allele. Sal1p is probably responsible for net uptake of ATP into mitochondria of cells with inhibited AACp. This putative function of yeast Sal1p is supported by investigation of human homologues of Sal1p, which exhibit ATP-Mg/P i exchange activity when they were reconstituted into liposomes (Fiermonte, G. et al., 2004). We have further characterized properties of isolated mitochondria with or without Sal1p. Absence of Sal1p does not change significantly respiration or generation of membrane potential. Our data from measurement of adenine nucleotide transport demonstrate that Sal1p does not operate in ADP/ATP exchange mode.