Surveying nonvisual arrestins reveals allosteric interactions between functional sites

Arrestins are important scaffolding proteins that are expressed in all vertebrate animals. They regulate cell-signaling events upon binding to active G-protein coupled receptors (GPCR) and trigger endocytosis of active GPCRs. While many of the functional sites on arrestins have been characterized, the question of how these sites interact is unanswered. We used anisotropic network modeling (ANM) together with our covariance compliment techniques to survey all the available structures of the nonvisual arrestins to map how structural changes and protein-binding affect their structural dynamics. We found that activation and clathrin binding have a marked effect on arrestin dynamics, and that these dynamics changes are localized to a small number of distant functional sites. These sites include α-helix 1, the lariat loop, nuclear localization domain, and the C-domain β-sheets on the C-loop side. Our techniques suggest that clathrin binding and/or GPCR activation of arrestin perturb the dynamics of these sites independent of structural changes.     

Postcranial paleoneurology of the Diapsida

The relationships between the size of the spinal cord and the size of the neural canal, and between gross spinal cord anatomy and locomotor style, were documented in a wide range of living diapsids. Observed relationships were used to make predictions about spinal cord anatomy and about limb use and position in related fossil taxa. In particular, the data suggest that the brachial plexus, and therefore the cervical/dorsal vertebral transition, of the theropod dinosaurs studied was located considerably posterior to its presently accepted location, and that the forelimbs of the giant carnosaurs Tyrannosaurus rex and Carnotaurus sastrei were of biologically insignificant use. Neural canal measurements support previous interpretations of locomotor style in extinct crocodilians, and can be used to predict limb placement in plesiosaurs.     

The nucleotide sequence of oocyte 5S DNA in Xenopus laevis. II. The GC-rich region

The primary sequence of the GC-rich half of the repeating unit in X. laevis 5S DNA has been determined in both a single plasmid-cloned repeating unit and in the total population of repeatig units. The GC-rich half of the repeating unit contains a single long duplication of 174 nucleotides. The duplicated segment commences 73 nucleotides preceding the 5' end of the gene and terminates at nucleotide 101 of the gene. The duplicated portion of the gene, termed the pseudogene, differs by 10 nucleotides from the corresponding portion of the gene, and the remaining duplicated sequence of 73 nucleotides differs by 13 nucleotides. The plasmid-cloned repeating unit differs from the dominant sequence in the total population repeating units by 6 nucleotides in the GC-rich region. Evidence is provided that most of the CpG dinucleotides in 5S DNA are at least partially methylated.     

Maternal correlates of brood sex ratio variation in the lekking lance-tailed manakin Chiroxiphia lanceolata

Theory predicts that overall population sex ratios should be around parity. But when individual females can receive higher fitness from offspring of one sex, they may benefit by biasing their brood sex ratios accordingly. In lekking species, higher variance in male reproductive success relative to that of females predicts that male offspring gain disproportionately from favorable rearing conditions. Females should therefore produce male-biased broods when they are in a position to raise higher quality offspring: i.e., in better body condition or when they reproduce earlier in the breeding season. To investigate these hypotheses, we studied brood sex ratios of lance-tailed manakins Chiroxiphia lanceolata . We found that overall sex ratios and mean brood sex ratios were not different from random expectation. Brood sex ratios were not related to laying date or female body condition. However, we detected a quadratic relationship between brood sex ratios and maternal age: both young (1–2 years) and old (8+ years) females produced female-biased brood sex ratios. This relationship was most clear in a year also distinguished by early rainy and breeding seasons. We suggest that breeding inexperience in young females and senescence in older females is the most plausible explanation for these results, and that the relationship between female age and brood sex ratio is mediated by environmental conditions.     

Quantifying the evidence for ecological synergies

There is increasing concern that multiple drivers of ecological change will interact synergistically to accelerate biodiversity loss. However, the prevalence and magnitude of these interactions remain one of the largest uncertainties in projections of future ecological change. We address this uncertainty by performing a meta-analysis of 112 published factorial experiments that evaluated the impacts of multiple stressors on animal mortality in freshwater, marine and terrestrial communities. We found that, on average, mortalities from the combined action of two stressors were not synergistic and this result was consistent across studies investigating different stressors, study organisms and life-history stages. Furthermore, only one-third of relevant experiments displayed truly synergistic effects, which does not support the prevailing ecological paradigm that synergies are rampant. However, in more than three-quarters of relevant experiments, the outcome of multiple stressor interactions was non-additive (i.e. synergies or antagonisms), suggesting that ecological surprises may be more common than simple additive effects.