BIOENERGETICS

Author: VERAS PEIXOTO PABLO MARCO.
Year: 2005.
University: EXTREMADURA.
Place of defense: FACULTAD DE VETERINARIA.
Place of preparation: FACULTAD DE VETERINARIA.

Summary: Transport of proteins across the mitochondrial membrane is a vital process which depends for 98% of the mitochondrial proteins that are encoded in the nucleus. Three complex conveyors, TOM in the outer membrane, TIM23 and TIM 22 in the inner membrane are responsible for the distribution of these proteins in the four mitochondrial his compartment defined by the two membranes. The existence aqueous two channels, one related to the operation of TOM and another with the TIM23, has led us to raise the hypothesis that there was also an activity of channel-associated TIM22, the complex is not responsible for transport, but the insertion protein multiópicas in the mitochondrial inner membrane. Applying techniques clamping voltage directly on mitoplastos (mitochondria without outer membrane) and internal membranes reconstituted in liposomes, for the first time we have identified the conditions for the induction of this channel. Their electrophysiological characteristics are very similar wings described above for TOM and TIM23, but his distinction is made possible by the use of signal peptides specific. The channel TIM22 consists of two identical pores, whose opening is cooperative. The radius of each of these pores is large enough to accommodate up to two transmembrane helices. The molecular dissection of the complex TIM22 combined with the use of electrophysiological and biochemical techniques has enabled us to determine the role of each component of the complex in the structure and operation of its channel. Thus, we determined that the protein TIM 54 is not involved in either the structure or the operation of the channel. For its part, TIM22 is an essential component of the channel, while TIM 18 operate as a receiver delas internal signal sequences. Our results establish that TIM22 channel is dynamic, open only in the presence of the protein in transit. The progressive activation of this channel and the cooperative behavior of their multiple conductance levels are consistent with a channel latent, thinly covered by the electrochemical gradient. Also, the cooperative operation of its pores allow the insertion of the protein in the mitochondrial inner membrane, after possible desensambalaje the complex.

Author: GODOY RUIZ RAQUEL.
Year: 2006.
University: GRANADA.
Place of defense: FACULTAD DE CIENCIAS.
Place of preparation: UNIVERSIDAD DE GRANADA.

Summary: We have studied the effect of 27 mutations conservative (Glutamato-Aspartato and Valina-Isoleucina) on the thermodynamic stability of tiorredoxina E. Coli. Most of these mutations are destabilizing, indicating that the environments of the groups involved can be optimized with a high degree of specificity to the point discriminate between D, E, I and V. The corresponding interactions stabilizers could perhaps be detected in sequence alignments. This could be useful in the derivation of structural information from sequence alignments. The above results lead us to suggest the possibility of rationalizing and perhaps predict effects of mutations on the stability of proteins on the basis of 'evolutionary models. 'Evolutionary model' we mean a model for the effects of mutation on the stability, which assesses certain characteristics of the environment of the residue mutated, from the point of view of how these environments have been selected