F. Wang et Pl. Polavarapu, Temperature influence on the secondary structure of avidin and avidin-biotin complex: A vibrational circular dichroism study, J PHYS CH B, 105(32), 2001, pp. 7857-7864
Vibrational absorption and vibrational circular dichroism spectra of avidin
with and without d-biotin in phosphate buffer were recorded in the amide I
' (1800-1600 cm(-1)) region as a function of temperature. The differences
in the unfolding pathway of avidin in the presence and absence of biotin we
re examined using the curve-fitting results of absorption spectra, and the
variable-temperature absorption and VCD spectra. This study reveals, contra
ry to previous spectroscopic studies, but in agreement with X-ray structura
l studies, that avidin contains beta -sheet structures with turns and bends
, but does not contain a-helical structure. Also a cooperative structural t
ransition leading to formation of aggregated antiparallel beta -strands, wi
th increasing temperature, has been inferred. In avidin-biotin complex, how
ever, some reversible unfolding of beta -sheet structure is noted but a coo
perative structural transition has not been noted with increase in temperat
ure. Two-dimensional (2D)-VCD correlation spectroscopy has also been used t
o analyze the sequence of events in structural unfolding of avidin.