Protein-bound sulfhydryl groups and thiolesters in mitochondria and submitochondrial particles and their relationships to oxidative phosphorylation

Procedures are described for measurement of total protein-bound —SH groups and apparent thiolester linkages in mitochondrial preparations. The procedure for total —SH is based on reaction with radioactive p-mercuribenzoate in 6 m guanidine hydrochloride at pH 9 containing 1 m ammonia buffer. The procedure for apparent thiolesters is based on alkylation of available — SH groups in 6 m guanidine hydrochloride, protein precipitation with perchloric acid, and ammonolysis at pH 9 to liberate — SH from any thiolester present.No variations in total —SH groups measured in Submitochondrial particles or in mitochondria were noted with presence or absence of ATP, ADP, substrates, or uncouplers of oxidative phosphorylation. Previous reports of changes in measured — SH groups thus appear to reflect solely changes in the reactivity of — SH groups and not in the total — SH groups present.Submitochondrial particles contained less than 0.5 nmole of apparent thiolester per mg of protein; mitochondria contained 1 to 2 nmoles. No variation of apparent thiolester content was noted with change in conditions affecting oxidative phosphorylation. The data do not, of course, eliminate possible changes in thiolester content below the sensitivity of the detection procedures.     

The genetic structure of a tribal population,the Yanomama Indians. XII. Biodemographic studies

The Yanomama Indians of Southern Vanezuela and Northern Brazil are one of the largest, relatively unacculturated tribes of the tropical rain forest. Over a period of eight years data have been collected from a considerable portion of their territory on estimated age, sex ratio, fertility rates (as determined by physical examination and urine tests), and infant death rates. Although it has been impossible to collect direct data on infanticide, this subject can be approached indirectly through distortions of the sex ratio and anecdotal information. Some historical data are also available as a basis for estimating tribal expansion in the past 100 years. With this material it has been possible to construct Life Tables for the Yanomama, and to explore the results of various perturbations of the input parameters. Data are also presented on patterns of mating and reproduction: number of spouses, mean and variance in number of surviving children, frequency of “extra-marital conceptions” based on the results of extensive blood group typings, and consanguinity rates as determined by observation and computer simulation. Although we do not present the Yanomama as typical, these data are seen as providing a basis for more realistic population models than have existed in the past. In addition, the data provide a basis for relatively precise estimates of such demographic measures as Fisher's Reproductive Value, Crow's Index of Total Selection, and Weiss' Index of Growth Regulation.     

Electrophoretic profiles of cyanobacterial membrane polypeptides showing heme-dependent peroxidase activity

The photosynthetic membranes of Anacystis nidulans R2 were examined electrophoretically following solubilization with lithium dodecyl sulfate. Electrophoresis yielded six prominent chlorophyll-containing bands. In addition, five polypeptides were observed which possessed heme-dependent peroxidase activity, monitored by incubating gels with 3,3′,5,5′-tetramethylbenzidine plus hydrogen peroxide. One such polypeptide, at 105 kdaltons, was removed by repeated washing of the membranes. Four remaining peroxidase-active polypeptides were observed at 7.2, 13.5, 18.5 and 33 kdaltons. Further examination of these four polypeptides yielded the following results. (1) The mobility of the 33 kdalton polypeptide was altered from 29 to 33 kdaltons upon heating (70°C) during membrane solubilization. (2) All four polypeptides showed stable heme-protein associations in the presence of 8 M urea; however, in the presence of urea, alterations in protein mobility were observed for each poly-peptide and only two (at 13.5 and 33 kdaltons) showed peroxidase activity following heating (70°C) during membrane solubilization. (3) The presence of thiols during membrane solubilization at 0°C was required to observe peroxidase activity at 7.2 kdaltons. These results, when compared to known properties of isolated cytochromes, suggest that the four polypeptides characterized here correspond to the subunits of photosynthetic cytochromes. Electrophoretic assessment of maize mutants lacking cytochrome f and b₆ activity supports this suggestion.     

Interaction between the Effects of Inside and Outside Na and K on Bullfrog Skin Potential

The composition of the solution bathing one border of the isolated frog skin affects the response of the potential across the skin to changes in the composition of the solution bathing the opposite border. Increasing the K concentration of the inside (corium) bathing solution decreased the sensitivity of the potential to a change in outside Na concentration. Decreasing the outside Na concentration decreased the sensitivity of the potential to a change in inside K concentration. Increasing the total ionic strength of the outside bathing solution or of both bathing solutions decreased the sensitivity of the potential to a change in outside Na concentration.