Solubility characteristics of Micrococcus lysodeikticus membrane components in detergents and chaotropic salts analyzed by immunoelectrophoresis

In order to evaluate the effectiveness and selectivity of various reagents in the solubilization of bacterial membranes, membranes of Micrococcus lysodeikticus were treated with detergents and chaotropic agents. The composition of the extracts so obtained was analyzed by rocket and two-dimensional immunoelectrophoretic techniques. Recovery of succinate-, malate-, and reduced nicotinamide adenine dinucleotide- (NADH) dehydrogenases, ATPase, succinylated lipomannan and cytochromes in the extracts was measured. Treatment with a variety of non-denaturing detergents produced extracts that were generally qualitatively uniform although quantitative differences were observed. The degree of extraction of various components was correlated with the hydrophile-lipophile balance. Several chaotropic agents were also evaluated as reagents for membrane solubilization. These agents were less effective in extraction of bulk protein, but produced extracts enriched in some membrane components.     

Influence of rainfall on sleeping site choice by a group of anubis baboons (Papio anubis)

For diurnal nonhuman primates, shifting among different sleeping sites may provide multiple benefits such as better protection from predators, reduced risk of parasitic infection, and closer proximity to spatially and temporally heterogeneous food and water. This last benefit may be particularly important in sleeping site selection by primates living in savanna‐woodlands where rainfall is more limited and more seasonally pronounced than in rainforests. Here, we examined the influence of rainfall, a factor that affects food and water availability, on the use of sleeping sites by anubis baboons (Papio anubis) over two 13‐month study periods that differed in rainfall patterns. We predicted that during wet periods, when food and water availability should be higher, the study group would limit the number of sleeping sites and would stay at each one for more consecutive nights than during dry periods. Conversely, we predicted that during dry periods the group would increase the number of sleeping sites and stay at each one for fewer consecutive nights as they searched more widely for food and water. We also predicted that the group would more often choose sleeping sites closer to the center of the area used during daytime (between 07:00 and 19:00) during wet months than during dry months. Using Global Positioning System data from collared individuals, we found that our first prediction was not supported on either monthly or yearly timescales, although past monthly rainfall predicted the use of the main sleeping site in the second study period. Our second prediction was supported only on a yearly timescale. This study suggests that baboons’ choice of sleeping sites is fluid over time while being sensitive to local environmental conditions, one of which may be rainfall.     

Interdomain but not intermolecular interactions observed in CFTR channels.

Gating of the cystic fibrosis transmembrane conductance regulator (CFTR) channels requires interdomain and/or intermolecular interactions involving different parts of the protein, yet the exact nature of those interactions remains unclear. In this study we report that treating wild type CFTR-expressing cells with oxidizing agents results in a significant reduction in the gel mobility of the protein indicative of the formation of disulfide bonds. In contrast, mutant CFTR channels in which cysteine residues in both nucleotide binding domains (NBDs) were mutated to serine, showed little change in gel mobility in oxidizing conditions. Mutation of the two cysteine residues in either the first or the second NBD alone also eliminates the change in gel mobility in oxidizing conditions. Wild type channels treated with oxidizing agents did not appear to form disulfide bonds with other proteins, suggesting that the close association that allows the formation of disulfide bonds occurs only within single proteins and not between separate channels interacting in a multimer.     

Hinging of rabbit myosin rod

The question of hinging in myosin rod from rabbit skeletal muscle has been reexamined. Elastic light scattering and optical rotation have been used to measure the radius of gyration and fraction helix, respectively, as a function of temperature for myosin rod, light meromyosin (LMM), and long subfragment 2 (long S-2). The radius of gyration vs temperature profile of myosin rod is shifted with respect to the optical rotation melting curve by about -5 degrees C. Similar studies on both LMM and long S-2 show virtually superimposable profiles. To correlate changes in the secondary structure with the overall conformation, plots of radius of gyration vs fraction helix are presented for each myosin subfragment. Myosin rod exhibits a marked decrease in the radius of gyration from 43 nm to approximately 35 nm, while the fraction helix remains at nearly 100%. LMM and long S-2 did not show this behavior. Rather, a decrease in the radius of gyration of these fragments occurred with comparable changes in fraction helix. These results are interpreted in terms of hinging of the myosin rod within the LMM/S-2 junction.