Genetic mobility

The use of sequence information to frame structural, functional, and evolutionary hypotheses represents a major challenge for the postgeno-mic era. Central to an understanding of the evolution of sequence families is the concept of the domain a structurally conserved, genetically mobile unit. When viewed at the three-dimensional level of protein structure, a domain is a compact arrangement of secondary structures connected by linker polypeptides. It usually folds independently and possesses a relatively hydrophobic core (Janin and Chothia, 1985). The importance of domains is that they cannot be divided into smaller units— they represent a fundamental building block that can be used to understand the evolution of proteins. 

V. Domains in Diverse Molecular Contexts A. Genetic Mobility... 

Schultz, J., R. R. Copley, T. Doerks, C. R Ponting, and P. Bork. 2000. SMART A web-based tool for the study of genetically mobile domains. Nucleic Acids Res 28 231-4. 

Cooper A. A., Stevens T. H. (1995) Protein splicing self-splicing of genetically mobile elements at the protein level. Trends Bioc. Sciences 20 351. 

The situation in which domain homologs are present in proteins with different domain compositions and arrangements is assumed to have arisen through intragenomic duplication and recombination events. Such genetically mobile domains are also sometimes called modules. This term was originally introduced into the protein world in the context of immunoglobulin domains, but was later used to describe packed... 

ACLAME http //aclame.ulb.ac.be/ Genetic mobile elements... 

Roberts MC- Tetracycline resistance determinants—mechanisms of action, regulation of expression, genetic mobility, and distribution. FEMS Microbiol Rev 1996 19 1-24-... 

FIGURE 1.25 The virus life cycle. Viruses are mobile bits of genetic iuformatiou encapsulated in a protein coat. The genetic material can be either DNA or RNA. Once this genetic material gains entry to its host cell, it takes over the host machinery for macromolecular synthesis and subverts it to the synthesis of viral-specific nucleic acids and proteins. These virus components are then assembled into mature virus particles that are released from the cell. Often, this parasitic cycle of virus infection leads to cell death and disease. 

Over 4 decades, between 1960 and 2000, the development of new antibiotics used well characterized basic structures for partial synthetic modifications, primarily to overcome resistance by increasing the pharmacodynamic properties and, secondarily, to improve the pharmacokinetic profile of older compounds. However, bacteria rapidly responded by acquiring additional genetic alterations either as mutations or by accumulating resistance genes as part of mobile genetic elements ( integrons) on transferable resistance plasmids. 

Transposons are mobile DNA elements (sizes 2.5-23 kbp) that move from one place to another in the chromosome or onto extrachromosomal genetic elements within the same cell. They are flanked by inverted repeats at then-ends and encode among other proteins a transposase that is needed for the transposition process. Resistance genes in the transposon are often parts of integrons. These are structures that cany an integrase responsible for the insertion of the resistance gene cassettes into the integron. 

The evolutionary history of symbiotic nitrogen fixers is therefore a tale of coevolution, which occurred in the shadow of their hosts, chasing their growing roots, and striving for adaptation. It is an example of how bacterial genetics has managed to keep pace with the creative power of eukaryotic sexual recombination. Mobile replicons, insertion elements, and symbiotic islands prone to move have helped rhizobia to succeed in their pursuit. The race, naturally, is not over and, looking at it from a distance, what we have. seen, compared to what we have yet to see, is probably just a cloud of dust. 

Nojiri H, Shintani M, Omori T (2004) Divergence of mobile genetic elements involved in the distribution of xenobiotic-catabolic capacity. Appl Microbiol Biotechnol 64 154-174... 

Top EM, Springael D (2003) The role of mobile genetic elements in baderial adaptation to xenobiotic organic compounds Curr Opin Biotechnol 14 262-269... 

Springael D, Top EM (2004) Horizontal gene transfer and microbial adaptation to xenobio-tics new types of mobile genetic elements and lessons from ecological studies. Trends Microbiol 12 53-58... 

Top EM, Springael D, Boon N (2002) Catabolic mobile genetic elements and their potential use in bioremediation of polluted soils and waters. FEMS Microbiol Ecol 42 199-208... 

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