The cycling between GDP- and GTP- bound forms of the Ras protein is partly regulated by the binding of Sos. The structural/dynamic behavior of the complex formed between activated Sos and Ras at the point of the functional cycle where the nucleotide exchange is completed has not been described to date. Here we show that solution NMR spectra of H-Ras∙GTPγS mixed with a functional fragment of Sos...

Ras activation is crucial for lymphocyte development and effector function. Both T and B lymphocytes contain two types of Ras activators: ubiquitously expressed SOS and specifically expressed Ras guanyl nucleotide-releasing protein (RasGRP). The need for two activators is enigmatic since both are activated following antigen receptor stimulation. In addition, RasGRP1 appears to be dominant over ...

The SOS response is a DNA damage response pathway that serves as a general safeguard of genome integrity in bacteria. Extensive studies of the SOS response in Escherichia coli have contributed to establishing the key concepts of cellular responses to DNA damage. However, how the SOS response impacts on the dynamics of DNA replication fork movement remains unknown. We found that inducing the SOS...

We formulate the sensor network localization problem as finding the global minimizer of a quartic polynomial. Then sum of squares (SOS) relaxations can be applied to solve it. However, the general SOS relaxations are too expensive to implement for large problems. Exploiting the special features of this polynomial, we propose a new structured SOS relaxation, and discuss its various properties. W...

The Ras-specific nucleotide exchange factor Son of sevenless (Sos) is inactive without Ras bound to a distal allosteric site. In contrast, the catalytic domain of Ras guanine nucleotide releasing factor 1 (RasGRF1) is active intrinsically. By substituting residues from RasGRF1 into Sos, we have generated mutants of Sos with basal activity, partially relieved of their dependence on allosteric ac...

The SOS system and SOS mutagenesis are frequently studied, or exploited to obtain an increase in mutagenicity of bacteria. Here a short survey is made of the phenomenon of SOS response with special attention to latest and less discussed data, especially the induction of the SOS system in response to cell starvation or mutation of certain genes and the role of inducible DNA polymerases.

Systems of Systems (SoS) are a current focus of many organizations interested in integrating assets and utilizing new technology to create multi-component systems that deliver value over time. The dynamic composition of SoS along with the managerial independence of their component systems necessitates systems engineering considerations and methods beyond those of traditional systems engineering...

The ongoing changes in vegetation spring phenology in temperate/cold regions are widely attributed to temperature. However, in arid/semiarid ecosystems, the correlation between spring temperature and phenology is much less clear. We test the hypothesis that precipitation plays an important role in the temperature dependency of phenology in arid/semiarid regions. We therefore investigated the in...

Introduction The aim of the study was to establish reference data for tibia and radius bone ultrasonic speed of sound (SOS) measurement in our pediatric population, and to compare the results with original (built-in) reference data. We also investigated the relationship between SOS Z-scores and anthropometric parameters and bone markers. Method SOS was measured in 463 healthy children (1– 16 ye...