Free fatty acids activate a vigorous Ca(2+):2H(+) antiport activity in yeast mitochondria.

The accumulation and retention of Ca(2+) by yeast mitochondria (Saccharomyces cerevisiae) mediated by ionophore ETH 129 occurs with a variable efficiency in different preparations. Ineffective Ca(2+) transport and a depressed membrane potential occur in parallel, are exacerbated in parallel by exogenous free fatty acids, and are corrected in parallel by the addition of bovine serum albumin. Bovine serum albumin is not required to develop a high membrane potential when either Ca(2+) or ETH 129 are absent, and when both are present membrane potential is restored by the addition of EGTA in a concentration-dependent manner. Respiration and swelling data indicate that the permeability transition pore does not open in yeast mitochondria that are treated with Ca(2+) and ETH 129, whereas fatty acid concentration studies and the inaction of carboxyatractyloside indicate that fatty acid-derived uncoupling does not underlie the other observations. It is concluded that yeast mitochondria contain a previously unrecognized Ca(2+):2H(+) antiporter that is highly active in the presence of free fatty acids and leads to a futile cycle of Ca(2+) accumulation and release when exogenous Ca(2+) and ETH 129 are available. It is also shown that isolated yeast mitochondria degrade their phospholipids at a relatively rapid rate. The activity responsible is also previously unrecognized. It is Ca(2+)-independent, little affected by the presence or absence of a respiratory substrate, and leads to the hydrolysis of ester linkages at both the sn-1 and sn-2 positions of the glycerophospholipids. The products of this activity, through their actions on the antiporter, explain the variable behavior of yeast mitochondria treated with Ca(2+) plus ETH 129.     

Rapid development of cleaning behaviour by Torresian crows Corvus orru on non-native banteng Bos javanicus in northern Australia

In this paper we report the observation of a rapidly developed vertebrate symbiosis involving ectoparasite cleaning by a native corvid of northern Australia, the Torresian crow Corvus orru , on a recently introduced bovid ungulate, the banteng Bos javanicus . Facultative symbioses benefiting both participants (mutualisms) between birds and mammals appear to be rare, despite the apparent advantages obtained by the participants (ecto-parasite removal from the host and food provision to the cleaner). On three separate dates we observed a total of four C. orru individuals eliciting facilitation behaviours by a total of ten female banteng to assist in the removal of ectoparasites. Our observations document the first-known incidence of facultative cleaning behaviour by a native bird species on a non-native, wild vertebrate that has developed in approximately 150 years since the banteng's introduction to Australia.     

Characterization of complementary deoxyribonucleic acid for human adrenocortical 17 alpha-hydroxylase: a probe for analysis of 17 alpha-hydroxylase deficiency

To provide a basis for investigation of the molecular mechanisms underlying the hormonal regulation of steroid 17 alpha-hydroxylase (P-450 17 alpha) activity in adrenal, ovary, and testis as well as human 17 alpha-hydroxylase deficiency, we have isolated from a human fetal adrenal cDNA library a cDNA sequence complementary to the mRNA that encodes the human P-450 17 alpha enzyme. Of 75,000 colonies from the library that were screened by use of a nick-translated 5'-specific bovine P-450 17 alpha cDNA probe, 10 positive colonies were isolated and the clone with the longest insert (pcD-17 alpha H) was selected for further characterization. pcD-17 alpha H encodes the complete human P-450 17 alpha protein having approximately 78% homology at the nucleotide level and 71% homology at the amino acid level when the sequence of pcD-17 alpha H is compared to the bovine P-450 17 alpha cDNA sequence. By transient expression of the human P-450 17 alpha cDNA clone in COS 1 cells, we have demonstrated that the 17 alpha-hydroxylase and 17,20 lyase activities reside within the same human P-450 17 alpha polypeptide chain. The insert was also used as a probe to investigate, by means of Southern blot analysis, possible alterations in the P-450 17 alpha gene sequence in DNA isolated from skin fibroblasts from three patients with clinically characterized 17 alpha-hydroxylase deficiencies. No changes were detected in the DNA of any of the patients by this analysis.     

Structure of porcine heart cytoplasmic malate dehydrogenase: combining X-ray diffraction and chemical sequence data in structural studies

The amino acid sequence of cytoplasmic malate dehydrogenase (sMDH) has been determined by a combination of X-ray crystallographic and chemical sequencing methods. The initial molecular model incorporated an "X-ray amino acid sequence" that was derived primarily from an evaluation of a multiple isomorphous replacement phased electron density map calculated at 2.5-A resolution. Following restrained least-squares crystallographic refinement, difference electron density maps were calculated from model phases, and attempts were made to upgrade the X-ray amino acid sequence. The method used to find the positions of peptides in the X-ray structure was similar to those used for studying protein homology and was shown to be successful for large fragments. For sMDH, X-ray methods by themselves were insufficient to derive a complete amino acid sequence, even with partial chemical sequence data. However, for this relatively large molecule at medium resolution, the electron density maps were of considerable help in determining the linear position of peptide fragments. The N-acetylated polypeptide chain of sMDH has 331 amino acids and has been crystallographically refined to an R factor of 19% for 2.5-A resolution diffraction data.