Zinc-binding motif containing conserved cysteines and a histidine. Always found C-terminal to PH domains. The crystal structure [1] shows this motif packs against the PH domain. The PH+Btk module pair has been called the Tec homology (TH) region [3].

1: Structure of the PH domain and Btk motif from Bruton's tyrosine kinase: molecular explanations for X-linked agammaglobulinaemia. Hyvonen M, Saraste M; EMBO J 1997;16:3396-3404. PMID:9218782

2: Missense mutations affecting a conserved cysteine pair in the TH domain of Btk. Vihinen M, Nore BF, Mattsson PT, Backesjo CM, Nars M, Koutaniemi S, Watanabe C, Lester T, Jones A, Ochs HD, Smith CI; FEBS Lett 1997;413:205-210. PMID:9280283

3: Tec homology (TH) adjacent to the PH domain. Vihinen M, Nilsson L, Smith CI; FEBS Lett 1994;350:263-265. PMID:8070576