Identifying and Quantitating FAD and FMN in Simple and in Iron-Sulfur-Containing Flavoproteins

Abstract

The number of known flavin-containing proteins is steadily increasing thanks to the combination of several factors. Among them the following may be of particular interest: (1) increasing power of separation techniques and of molecular biology tools for overproduction of various proteins, and (2) recognition of putative flavin-dependent proteins through analysis of amino acid sequences deduced from those of (putative) genes discovered through genome-sequencing projects. Particularly interesting is the fact that novel flavin-dependent proteins, which play roles different from electron transport or redox catalysis are being discovered (e.g., gene transcription regulation as in the case of NifL, ()). On the other hand, the picture can be complicated by the fact that the same protein may harbor one or more flavin nucleotides plus one or more additional cofactors (). Among such nonflavin centers iron-sulfur clusters are common.