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The Xanthan Gum Polysaccharide Biosynthesis/Export, GumE (GumE) Family. 

GumE is a protein of 432 aas with 12 TMSs in a 5 + 4 + 3 TMS arrangement. it is involved, probably in a complex, in xanthan gum biosynthesis and export (Bianco et al. 2014). The family is diverse with proteins from many prokaryotes.  They may be exo-polysaccharide polymerases.

References associated with 9.B.30 family:

Bianco, M.I., M. Jacobs, S.R. Salinas, A.G. Salvay, M.V. Ielmini, and L. Ielpi. (2014). Biophysical characterization of the outer membrane polysaccharide export protein and the polysaccharide co-polymerase protein from Xanthomonas campestris. Protein Expr Purif 101: 42-53. 24927643