Structure of the fucose mutarotase fromStreptococcus pneumoniaein complex withL-fucose

Abstract

Streptococcus pneumoniaerelies on a variety of carbohydrate-utilization pathways for both colonization of its human host and full virulence during the development of invasive disease. One such pathway is the fucose-utilization pathway, a component of which is fucose mutarotase (SpFcsU), an enzyme that performs the interconversion between α-L-fucose and β-L-fucose. This protein was crystallized and its three-dimensional structure was solved in complex with L-fucose. The structure shows a complex decameric quaternary structure with a high overall degree of structural identity toEscherichia coliFcsU (EcFcsU). Furthermore, the active-site architecture ofSpFcsU is highly similar to that ofEcFcsU. When considered in the context of the fucose-utilization pathway found inS. pneumoniae,SpFcsU appears to link the two halves of the pathway by enhancing the rate of conversion of the product of the final glycoside hydrolysis step, β-fucose, into the substrate for the fucose isomerase, α-fucose.