A Modular Mathematical Model of Exercise-Induced Changes in Metabolism, Signaling, and Gene Expression in Human Skeletal Muscle.

Skeletal muscle is the principal contributor to exercise-induced changes in human metabolism. Strikingly, although it has been demonstrated that a lot of metabolites accumulating in blood and human skeletal muscle during an exercise activate different signaling pathways and induce the expression of many genes in working muscle fibres, the systematic understanding of signaling-metabolic pathway interrelations with downstream genetic regulation in the skeletal muscle is still elusive. Herein, a physiologically based computational model of skeletal muscle comprising energy metabolism, Ca2+, and AMPK (AMP-dependent protein kinase) signaling pathways and the expression regulation of genes with early and delayed responses was developed based on a modular modeling approach and included 171 differential equations and more than 640 parameters. The integrated modular model validated on diverse including original experimental data and different exercise modes provides a comprehensive in silico platform in order to decipher and track cause-effect relationships between metabolic, signaling, and gene expression levels in skeletal muscle.

Genome-Wide Atlas of Promoter Expression Reveals Contribution of Transcribed Regulatory Elements to Genetic Control of Disuse-Mediated Atrophy of Skeletal Muscle.

The prevention of muscle atrophy carries with it clinical significance for the control of increased morbidity and mortality following physical inactivity. While major transcriptional events associated with muscle atrophy-recovery processes are the subject of active research on the gene level, the contribution of non-coding regulatory elements and alternative promoter usage is a major source for both the production of alternative protein products and new insights into the activity of transcription factors. We used the cap-analysis of gene expression (CAGE) to create a genome-wide atlas of promoter-level transcription in fast (m. EDL) and slow (m. soleus) muscles in rats that were subjected to hindlimb unloading and subsequent recovery. We found that the genetic regulation of the atrophy-recovery cycle in two types of muscle is mediated by different pathways, including a unique set of non-coding transcribed regulatory elements. We showed that the activation of "shadow" enhancers is tightly linked to specific stages of atrophy and recovery dynamics, with the largest number of specific regulatory elements being transcriptionally active in the muscles on the first day of recovery after a week of disuse. The developed comprehensive database of transcription of regulatory elements will further stimulate research on the gene regulation of muscle homeostasis in mammals.

Expression and molecular characterization of the Mycobacterium tuberculosis PII protein.

The signal transduction protein PII plays an important role in cellular nitrogen assimilation and regulation. The molecular characteristics of the Mycobacterium tuberculosis PII (Mtb PII) were investigated using biophysical experiments. The Mtb PII coding ORF Rv2919c was cloned and expressed in Escherichia coli. The binding characteristics of the purified protein with ATP and ADP were investigated using surface plasmon resonance (SPR) and isothermal titration calorimetry (ITC). Mtb PII binds to ATP strongly with K(d) in the range 1.93-6.44 microM. This binding strength was not significantly affected by the presence of 2-ketoglutarate even in molar concentrations of 66 (ITC) or 636 (SPR) fold excess of protein concentration. However, an additional enthalpy of 0.3 kcal/mol was released in presence of 2-ketoglutarate. Binding of Mtb PII to ADP was weaker by an order of magnitude. Binding of ATP and 2-ketoglutarate were analysed by docking studies on the Mtb PII crystal structure (PDB id 3BZQ). We observed that hydrogen bonds involving the gamma-phosphate of ATP contribute to enhanced binding of ATP compared with ADP. Glutaraldehyde crosslinking showed that Mtb PII exists in homotrimeric state which is consistent with other PII proteins. Phylogenetic analysis showed that Mtb PII consistently grouped with other actinobacterial PII proteins.

Phylogenetic analysis of the p53 and p63/p73 gene families.

Proteins of the relative families p53 and p63/p73 are transcriptional factors that are involved in the signaling pathway in cells. The wide spectrum of their functions includes cell cycle arrest and apoptosis in response to DNA damage. The p53 protein also participates in development of particular tissues during embryogenesis. Thus, it is of high importance to establish the relation between structure, function and evolution of these proteins. In the current computational study, the evolutionary mode of the p63/p73 protein family is investigated. Search for the adaptive branches of the phylogenetic tree and the adaptive codons in the nucleotide sequences was performed using the codem1 program from the PAML package, version 3.14. The results obtained were compared with those of our previous phylogenetic analysis of the p53 protein. Evidence was obtained that the evolutionary history of the p63/p73 proteins has been under positive selection. An attempt is made to associate the current evidence with the previous for positive selection in the p53 family. Recently the G245C substitution has been assumed to result in formation of a novel Zn(2+)-binding site in the p53 protein. The molecular mechanics simulations were performed to estimate energy of zinc binding to its site in two dominant-negative p53 mutants--G245C and R175H--in comparison with the wild-type p53. The results of the estimation provided evidence of the novel Zn(2+)-binding site functionality in G245C mutant form.

PDBSite: a database of the 3D structure of protein functional sites.

The PDBSite database provides comprehensive structural and functional information on various protein sites (post-translational modification, catalytic active, organic and inorganic ligand binding, protein-protein, protein-DNA and protein-RNA interactions) in the Protein Data Bank (PDB). The PDBSite is available online at http://wwwmgs.bionet.nsc.ru/mgs/gnw/pdbsite/. It consists of functional sites extracted from PDB using the SITE records and of an additional set containing the protein interaction sites inferred from the contact residues in heterocomplexes. The PDBSite was set up by automated processing of the PDB. The PDBSite database can be queried through the functional description and the structural characteristics of the site and its environment. The PDBSite is integrated with the PDBSiteScan tool allowing structural comparisons of a protein against the functional sites. The PDBSite enables the recognition of functional sites in protein tertiary structures, providing annotation of function through structure. The PDBSite is updated after each new PDB release.

PDBSiteScan: a program for searching for active, binding and posttranslational modification sites in the 3D structures of proteins.

PDBSiteScan is a web-accessible program designed for searching three-dimensional (3D) protein fragments similar in structure to known active, binding and posttranslational modification sites. A collection of known sites we designated as PDBSite was set up by automated processing of the PDB database using the data on site localization in the SITE field. Additionally, protein-protein interaction sites were generated by analysis of atom coordinates in heterocomplexes. The total number of collected sites was more than 8100; they were assigned to more than 80 functional groups. PDBSiteScan provides automated search of the 3D protein fragments whose maximum distance mismatch (MDM) between N, Calpha and C atoms in a fragment and a functional site is not larger than the MDM threshold defined by the user. PDBSiteScan requires perfect matching of amino acids. PDBSiteScan enables recognition of functional sites in tertiary structures of proteins and allows proteins with functional information to be annotated. The program PDBSiteScan is available at http://wwwmgs.bionet.nsc.ru/mgs/systems/fastprot/pdbsitescan.html.