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Structure--function relationships of the membrane-embedded Saccharomyces cerevisiae mitochondrial ADP/ATP carrier are investigated through proteolysis and cysteine labeling approaches. It is indicated that the matrix loop m2 connecting the transmembrane helices H3 to H4 intrudes to some extent into the inner mitochondrial membrane.

Research has been conducted on mitochondrial adenine nucleotide carrier. The study of the human mitochondrial adenine nucleotide carrier coding gene expression in yeast Saccharomyces cerevisiae triple mutant has been carried out, and the ADP/ATP exchange kinetics of the human carriers has been analyzed and discussed.

Synthesis of a photoactivable ADP analogue 2-azido-3'-O-naphthoyl-[beta-(sup)32P]ADP and its use to map nucleotide binding sites of the ADP/ATP carrier in membranes is presented. Results demonstrate the existence of two ADP/ATP carrier regions in yeast mitochondrial membrane systems that are involved in substrate recognition.

The fluorometric approach was utilized to assess the conformational changes of mitochondrial adenine nucleotide carrier (Ancp) during the process of cellular transport. Mutated ANC2 genes with tyrosine codons in JLI-3 Saccharomyces cerevisiae strains exhibited normal growth on glycerol due to the presence of active Anc2p. However, longer growth doubles and la phases were detected in yeast strains expressing doubly or triply substituted ANC2 genes.

The adenosine diphosphate/adenosine triphosphate (ADP/ATP) carrier protein (Ancp) exhibits fluorescence changes during the process of cellular transport and protein folding. The intrinsic fluorescence of tryptophanyl residues of two Ancp such as Trp235 and Trp126 were affected by carboxyatractyloside, adenosine triphosphate and bongkreik acid. Furthermore, the Trp87 and Trp126 residues enhanced the fluorescence of Anc2p during ATP binding.

A study was done on the 23-kilodalton protein which is a substrate of protein kinase C. It was shown that p23 show large primary structure homologies with the human proteins MRP14 and MRP8 which are expressed in large amounts during chronic inflammation. It also cross-reacted with monoclonal antibodies specific for these human proteins. The association of p23 with p7 results to the formation of a heterodimeric complex which are tolerant of trypsin. These properties closely resemble those of proteins belonging to the S100 family.

The complete alignment of the 63 residues of the mitochondrial ATPase inhibitor from the yeast Candida utilis has been determined. The sequence study was carried out mainly by automatic (liquid and solid-phase) methods. Peptides were obtained by enzymatic digestion with clostripain and purified by reverse-phase high-performance liquid chromatography. The ATPase inhibitor contains three sets of repetitive sequences and eight clusters of charged residues, as also found in the inhibitor of Saccharornyces cerevisiae, with which it shares 58.7% homology of conserved residues. When the two yeast ATPase inhibitor sequences were compared to that of beef heart, 20 residues remained common to the three alignments, although the latter protein contained a long histidine-rich insertion, only found in this inhibitor. Most of the homologous residues were clustered near the center of the protein, which by partial proteolytic digestion of the beef heart ATPase inhibitor [Dianoux, A. C. et al. (1982) FEBS Lett. 140, 223-228] has already been shown to be involved in the biological function. [ABSTRACT FROM AUTHOR]

A product of mitochondrial protein synthesis in rat liver mitochondria, characterized by a low molecular weight (Mr < 10000) and an unusually high hydrophobicity, has been identified as the dicyclohexylcarbodiimide-binding protein and as a peptide of the hydrophobic sector of the mitochondrial ATPase complex. The purified protein still possesses the ability to bind dicyclohexylcarbodiimide. [ABSTRACT FROM AUTHOR]

A low molecular weight product (Mr 7000) synthetized on rat liver mitoribosomes is selectively extracted by chloroform/methanol (&frac21;). This products characterized by an unusual hydrophobicity, as reflected by its chromatographic behaviour, its high content in hydrophobic amino acids and its strong capacity to bind lipids. Bound lipids contain a high percentage of linoleic acid. [ABSTRACT FROM AUTHOR]

I. This paper describes some features of the protein synthesis in isolated rat liver mitochondria and reports on the stability of the product of mitochondrial protein synthesis in vitro. 2. Chase experiments performed after a 30-min pulse of [14C]leucine indicated that a large part of the product is degraded to an acid-soluble form (labile product) almost as rapidly as it is terminated and released from the mitoribosome. Only a small proportion of the completed product (between 20 and 40 %)is conversed in acid-insoluble form (stable product). 2. Both labile and stable products have an exceptional degree of hydrophobicity, shown by their marked resistance to acid and alkaline hydrolysis and by their solubility in organic solvents. 4. A 14C-labelled peptide with an apparent molecular weight of 12000-13000, as assessed by gel electrophoresis in the presence of dodecylsulfate, is released after heat treatment of mitoribosomes isolated from mitochondria pulsed with [14C]leucine. [ABSTRACT FROM AUTHOR]