Screening of a Highly Soluble and Oxygen-independent Blue Fluorescent Protein from Metagenome

GFP and its derivatives are commonly used as non-invasive in vivo reporters. These fluorescent proteins have been employed to analyze expression level, localization and movement of proteins, as well as protein interaction. However, they cannot be utilized under anaerobic conditions due to the oxygen requirement for the maturation of the fluorophore. Thus, other proteins with a different mechanism of fluorescence emission are needed. We reported here a blue fluorescent protein, named mBFP, that was derived from metagenomic DNA. This protein consisting of 248 amino acids was overexpressed (>35% of the total protein) in a soluble form in Escherichia coli. mBFP showed a distinct fluorescence pattern that was NADPH-dependent and could be used to image live cells under anaerobic conditions. Thus, mBFP holds great promise for use as a reporter in a broad range of applications.