pone.0259900.g001.tif (2.67 MB)

Group four capsule operon and GfcD.

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posted on 2021-11-15, 18:40 authored by Matthew R. Larson, Kassia Biddle, Adam Gorman, Sarah Boutom, Ilan Rosenshine, Mark A. Saper

(a) The Escherichia coli group 4 operon consists of seven genes. The genes gfcA, gfcB, gfcC, and gfcD encode proteins of an unknown function. Genes gfcE, etp, and etk share homology with proteins of Group 1 capsule export systems. Distant homologs are also found in Vibrio and Burkholderia species. (b) Membrane topology of GfcD as predicted by HHOMP and classified as a potential outer membrane β-barrel protein. The central region (273–427) is devoid of transmembrane strands and may be an independently folded domain with the predicted secondary structure shown. The signal sequence at the N-terminus (shaded blue) shows a putative signal peptidase II cleavage and acylation site (arrow 19) as previously annotated, and the peptidase I cleavage site (arrow 22) revealed in the present work by MALDI-TOF and N-terminal sequencing.