Surface dynamics in allosteric regulation of protein-protein interactions: modulation of calmodulin functions by Ca2+.

Knowledge of the structural basis of protein-protein interactions (PPI) is of fundamental importance for understanding the organization and functioning of biological networks and advancing the design of therapeutics which target PPI. Allosteric modulators play an important role in regulating such interactions by binding at site(s) orthogonal to the complex interface and altering the protein's propensity for complex formation. In this work, we apply an approach recently developed by us for analyzing protein surfaces based on steered molecular dynamics simulation (SMD) to the study of the dynamic properties of functionally distinct conformations of a model protein, calmodulin (CaM), whose ability to interact with target proteins is regulated by the presence of the allosteric modulator Ca(2+). Calmodulin is a regulatory protein that acts as an intracellular Ca(2+) sensor to control a wide variety of cellular processes. We demonstrate that SMD analysis is capable of pinpointing CaM surfaces implicated in the recognition of both the allosteric modulator Ca(2+) and target proteins. Our analysis of changes in the dynamic properties of the CaM backbone elicited by Ca(2+) binding yielded new insights into the molecular mechanism of allosteric regulation of CaM-target interactions.

MitoBamAnnotator: A web-based tool for detecting and annotating heteroplasmy in human mitochondrial DNA sequences.

The use of Next-Generation Sequencing of mitochondrial DNA is becoming widespread in biological and clinical research. This, in turn, creates a need for a convenient tool that detects and analyzes heteroplasmy. Here we present MitoBamAnnotator, a user friendly web-based tool that allows maximum flexibility and control in heteroplasmy research. MitoBamAnnotator provides the user with a comprehensively annotated overview of mitochondrial genetic variation, allowing for an in-depth analysis with no prior knowledge in programming.

Plant response to stress meets dedifferentiation.

Plant response to various stress conditions often results in expression of common genes, known as stress-responsive/inducible genes. Accumulating data point to a common, yet elusive process underlying the response of plant cells to stress. Evidence derived from transcriptome profiling of shoot apical meristem stem cells, dedifferentiating protoplast cells as well as from senescing cells lends support to a model in which a common response of cells to certain biotic and abiotic stresses converges on cellular dedifferentiation whereby cells first acquire a stem cell-like state before assuming a new fate.

Autosomal recessive hyponatremia due to isolated salt wasting in sweat associated with a mutation in the active site of Carbonic Anhydrase 12.

Genetic disorders of excessive salt loss from sweat glands have been observed in pseudohypoaldosteronism type I (PHA) and cystic fibrosis that result from mutations in genes encoding epithelial Na+ channel (ENaC) subunits and the transmembrane conductance regulator (CFTR), respectively. We identified a novel autosomal recessive form of isolated salt wasting in sweat, which leads to severe infantile hyponatremic dehydration. Three affected individuals from a small Bedouin clan presented with failure to thrive, hyponatremic dehydration and hyperkalemia with isolated sweat salt wasting. Using positional cloning, we identified the association of a Glu143Lys mutation in carbonic anhydrase 12 (CA12) with the disease. Carbonic anhydrase is a zinc metalloenzyme that catalyzes the reversible hydration of carbon dioxide to form a bicarbonate anion and a proton. Glu143 in CA12 is essential for zinc coordination in this metalloenzyme and lowering of the protein-metal affinity reduces its catalytic activity. This is the first presentation of an isolated loss of salt from sweat gland mimicking PHA, associated with a mutation in the CA12 gene not previously implicated in human disorders. Our data demonstrate the importance of bicarbonate anion and proton production on salt concentration in sweat and its significance for sodium homeostasis.

KinSNP software for homozygosity mapping of disease genes using SNP microarrays.

Consanguineous families affected with a recessive genetic disease caused by homozygotisation of a mutation offer a unique advantage for positional cloning of rare diseases. Homozygosity mapping of patient genotypes is a powerful technique for the identification of the genomic locus harbouring the causing mutation. This strategy relies on the observation that in these patients a large region spanning the disease locus is also homozygous with high probability. The high marker density in single nucleotide polymorphism (SNP) arrays is extremely advantageous for homozygosity mapping. We present KinSNP, a user-friendly software tool for homozygosity mapping using SNP arrays. The software searches for stretches of SNPs which are homozygous to the same allele in all ascertained sick individuals. User-specified parameters control the number of allowed genotyping 'errors' within homozygous blocks. Candidate disease regions are then reported in a detailed, coloured Excel file, along with genotypes of family members and healthy controls. An interactive genome browser has been included which shows homozygous blocks, individual genotypes, genes and further annotations along the chromosomes, with zooming and scrolling capabilities. The software has been used to identify the location of a mutated gene causing insensitivity to pain in a large Bedouin family. KinSNP is freely available from.