TAA-head_Trp-ring is the tryptophan-ring motif of some Gram-negative Enterobacteriaceae. The Trp-ring folds into a beta-meander type on the top of the head domain of its trimeric autotransporter adhesin proteins. In conjunction with the GIN domain it is thought to be the region of the head that adheres to fibronectin.

1: Repetitive architecture of the Haemophilus influenzae Hia trimeric autotransporter. Meng G, St Geme JW 3rd, Waksman G; J Mol Biol. 2008;384:824-836. PMID:18948113

2: Domain annotation of trimeric autotransporter adhesins--daTAA. Szczesny P, Lupas A; Bioinformatics. 2008;24:1251-1256. PMID:18397894

3: Structure of a Burkholderia pseudomallei trimeric autotransporter adhesin head. Edwards TE, Phan I, Abendroth J, Dieterich SH, Masoudi A, Guo W, Hewitt SN, Kelley A, Leibly D, Brittnacher MJ, Staker BL, Miller SI, Van Voorhis WC, Myler PJ, Stewart LJ; PLoS One. 2010; [Epub ahead of print] PMID:20862217

4: Structure and biology of trimeric autotransporter adhesins. Lyskowski A, Leo JC, Goldman A; Adv Exp Med Biol. 2011;715:143-158. PMID:21557062