IIBBA   05544
INSTITUTO DE INVESTIGACIONES BIOQUIMICAS DE BUENOS AIRES
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
EXPERIMENTALLY APPROACHING THE SOLVENT ACCESSIBLE SURFACE AREA OF A PROTEIN
Autor/es:
PATRICIO CRAIG; GABRIELA GÓMEZ; DANIELA URETA; JULIO CARAMELO; JOSÉ M. DELFINO
Lugar:
Bariloche-Argentina
Reunión:
Workshop; US-Argentina Workshop on Nanomaterials; 2009
Institución organizadora:
US-Argentina Workshop on Nanomaterials
Resumen:
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EXPERIMENTALLY APPROACHING THE SOLVENT ACCESSIBLE SURFACE AREA OF A
PROTEIN
P.O. Craig, G.E. Gómez, D.B. Ureta, J.J. Caramelo, and J.M. Delfino
Departamento de
Química Biológica, Facultad de Farmacia y Bioquímica, Universidad de Buenos
Aires e Instituto de Química y Fisicoquímica Biológica (IQUIFIB-CONICET). Junín
956, C1113AAD Buenos Aires, Argentina.
e-mail: delfino@qb.ffyb.uba.ar
Abstract
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 (α-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 α-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.