Distinct Properties of Hexameric but Functionally Conserved Mycobacterium tuberculosis Transcription-Repair Coupling Factor

Transcription coupled nucleotide excision repair (TC-NER) is involved in correcting UV-induced damage and other road-blocks encountered in the transcribed strand. Mutation frequency decline (Mfd) is a transcription repair coupling factor, involved in repair of template strand during transcription. Mfd from M. tuberculosis (MtbMfd) is 1234 amino-acids long harboring characteristic modules for different activities. Mtbmfd complemented Escherichia coli mfd (Ecomfd) deficient strain, enhanced survival of UV irradiated cells and increased the road-block repression in vivo. The protein exhibited ATPase activity, which was stimulated ∼1.5-fold in the presence of DNA. While the C-terminal domain (CTD) comprising amino acids 630 to 1234 showed ∼2-fold elevated ATPase activity than MtbMfd, the N-terminal domain (NTD) containing the first 433 amino acid residues was able to bind ATP but deficient in hydrolysis. Overexpression of NTD of MtbMfd led to growth defect and hypersensitivity to UV light. Deletion of 184 amino acids from the C-terminal end of MtbMfd (MfdΔC) increased the ATPase activity by ∼10-fold and correspondingly exhibited efficient translocation along DNA as compared to the MtbMfd and CTD. Surprisingly, MtbMfd was found to be distributed in monomer and hexamer forms both in vivo and in vitro and the monomer showed increased susceptibility to proteases compared to the hexamer. MfdΔC, on the other hand, was predominantly monomeric in solution implicating the extreme C-terminal region in oligomerization of the protein. Thus, although the MtbMfd resembles EcoMfd in many of its reaction characteristics, some of its hitherto unknown distinct properties hint at its species specific role in mycobacteria during transcription-coupled repair

Synthesis, characterization and applications of amphiphilic elastomeric polyurethane networks in drug delivery

Polyurethanes have a key role in the development of many different biomedical devices because of their exceptional biocompatibility, mechanical properties and versatility. Although linear segmented polyurethanes have been extensively studied, the investigation of cross-linked polyurethanes remains limited. In this work, three series of polyurethane networks were synthesized by reacting poly(ethylene glycol) and hexamethylene diisocyanate with either tetrafunctional poloxamer Tetronic 701 or poly(e-caprolactone)s triol with molecular weights of 1060 and 3130 Da. The hydrophilic/hydrophobic ratio was varied by selecting the appropriate amounts of monomers, and its effects on the swelling behavior and the thermal properties were analyzed. Studies concerning the release of a model drug were performed, the results of which indicate that these materials hold promise for use in controlled implantable drug-delivery devices and antimicrobial coatings.Fil: Caracciolo, Pablo Christian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Mar del Plata. Instituto de Investigación en Ciencia y Tecnología de Materiales (i); Argentina;Fil: Sanz Pita, Cristina. Universidad de Girona. Grupo Lepamap; España;Fil: Abraham, Gustavo Abel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Mar del Plata. Instituto de Investigación en Ciencia y Tecnología de Materiales (i); Argentina;Fil: Méndez, José Alberto. Universidad de Girona. Grupo Lepamap; España;Fil: Gironés Molera, Jordi. Consejo Superior de Investigaciones Cientificas. Instituto de Ciencia y Tecnologıa de Polimeros; España