Fluorescent Study of the Conformational Properties of Myoglobin Structure

Abstract

Myoglobin is known to be the reference protein that is why the knowledge of the conformational behavior of the myoglobin-like structure is of common importance for understanding the mechanism of protein functioning. In this work fluorescence was used to study the pH- and ligand-induced conformational changes in sperm whale myoglobin and related structures — apomyoglobin (apo-Mb) and the complex of apo-Mb with protoporphyrin IX (PPIX-apo-Mb) which is a iron-free analog of Mb. The structural changes at the N-terminal and adjacent protein region were followed by the fluorescence of two invariant tryptophans of the A-helix, Trp7(A5) and Trpl4(A12), while those in the “active site”, the heme crevice, were followed by emission of PPIX. As distinct from the non-fluorescing heme, PPIX has an extensive fluorescence in the visible spectral region.