Analysis of Models of F-Actin Using fluorescence Resonance Energy Transfer Spectroscopy

Abstract

Fluorescence resonance energy transfer spectroscopy (FRET) has been widely used to determine distances ranging from 10 to 100A between amino acids within proteins. However, FRET is not very good at measuring atomic distances because it measures the distance between two probes attached to an amino acid but not the position of the amino acid itself. Therefore, one has to take into consideration the size of the probes used to interpret the FRET data. FRET compensates for that deficit by being particularly sensitive to changes in distance and therefore is suitable to study conformational change in proteins (dos Remedios and Moens 1995a, 1995b).In 1981, Taylor et al. (1981) used FRET to determine the radial coordinate of Cys-374 of actin and study the assembly of actin filament. Subsequently, several authors have used this method to determine the radii of Gln-41 (Kasprzak 1988) the nucleotide binding site (Miki et al. 1986b; Kasprzak 1988) Cys-lO (Miki et al. 1986) and Cys-374(Kasprzak 1988; Moens et al. 1994).When myosin 51 binds to actin filaments, the radial coordinate of Gln-41 increases by 3 A(Kasprzak 1988) and we showed that the radius of Cys-374 increases by approximately 4.5A (Moens et a1. 1997).