Structural Features of Allosteric Effects in Proteins Revealed by Resonance Raman Spectroscopy

by Prof. Teizo Kitagawa (University of Hyogo, Japan)

Thursday, February 2, 2012 from 16:00 to 17:00 (Asia/Kolkata)
at Colaba Campus ( AG-66 )

TIFR, Colaba Mumbai 400005

Description

Allostery is a key concept for understanding protein function and regulation, but its structural realities are little known. A typical example of allostery is seen in cooperative oxygen binding of hemoglobin (Hb), while there are many proteins that exhibit this effect in function. We applied resonance Raman spectroscopy to investigate structural features of allosteric effects in hemoglobin and gas sensor proteins.

Hb is a tetrameric protein consisting of two a and b subunits (a₂b₂). Since the relation between a quaternary structure and oxygen affinity of Hb has been investigated with all the physicochemical techniques available, detailed analysis on Hb is expected to give some fundamental understanding of allostery. Ultraviolet resonance Raman (UVRR) spectroscopy can provide the vibrational spectra of aromatic residues selectively and thus reflect their interactions at the subunit interfaces of Hb. Accordingly, we tried to evaluate the quaternary structure of Hb in terms of inter-subunit interactions revealed by UVRR spectroscopy, particularly for half-ligated human Hb. We will demonstrate that the inter-subunit interactions really induce the internal strain at the heme iron, which determines oxygen affinity, and also that the magnitude of strain is distinctly different between the a and b subunits of Hb.