Part:BBa_K1352011

Antigen 43 (sometimes called Ag43 or fluffing protein) is a phase-variable outer membrane protein encoded by flu gene. It is native to E.Coli K12 strain and is usually expressed at about 50, 000 copies/cell. Ag34 precursor is 1039 amino acids long and subsequently becomes cleaved into alpha and beta chains (499 and 488 amino acids long respectively). The beta subunit forms a β-barrel pore via which alpha-subunit translocates to the cell surface, and with which it remains non-covalently joined. The surface alpha chain can be released by a brief heat treatment at approx. 60oC.

Ag43 is an autotransporter protein, therefore it possesses all information necessary for translocation to the cell surface in its coding sequence.

Ag43 mediates autoaggregation, via a velcro-like mechanism (Heras et. al., 2014), and plays a role in E.coli biofilm formation.