INVESTIGADORES
GOMEZ Gabriela Elena
congresos y reuniones científicas
Título:
EXPERIMENTALLY APPROACHING THE SOLVENT ACCESSIBLE SURFACE AREA OF A PROTEIN
Autor/es:
P.O. CRAIG; G.E. GÓMEZ; D.B. URETA; J.J. CARAMELO; J.M. DELFINO
Lugar:
San Carlos De Bariloche
Reunión:
Workshop; US-Argentina Workshop on Nanomaterials; 2009
Institución organizadora:
UBA-UCLA
Resumen:
Each conformation of a protein is inextricably related to a defined extent of solvent exposure that in turn determines its stability. However, accurate measurement of the solvent accessible surface area (ASA) is ill defined for any state other than the native state N. We developed an experimental approach to this fundamental physical parameter through the reaction of the photochemical probe diazirine (DZN) with the polypeptide chain. By its size, it is conceivable that DZN would exert molecular mimicry of the aqueous solvent. In our laboratory we advanced this methodology to address unfolding transitions of single-domain proteins (1,3) and the contact surface of an antigen-antibody complex (2). We then focused on the structural characterization of non-native states of the paradigmatic protein alpha lactalbumin (á-LA). The covalent tagging resulting from the unspecific methylene carbene reaction allows not only to obtain a global estimate of ASA, but to map solvent accessibility along the amino acid sequence as well. A consistent linear correlation emerges between the extent of methylene carbene labeling (MCL) and the predicted solvent exposed area. By its mild apolar nature, DZN reveals structurally organized hydrophobic phases in the acid-stabilized state A of á-LA. Notwithstanding this fact, in a fashion similar to the N state, the A state also exhibits local regions where increased MCL likely points to the presence of packing defects (cavities) able to lodge the reagent.