This domain is found at the N-terminal end of Harmonin from humans (USH1C) and similar proteins from vertebrates. Harmonin is a master scaffold in the assembly of the Usher protein complexes present in the inner ear and the retina. Defects in these proteins are related to a hereditary hearing-vision loss disease, Usher syndrome I (USH1). The N-terminal domain of USH1C, which precedes the first PDZ protein- binding domain (Pfam:PF00595), adopts a compact five-helix-bundle structure [1,3].

1: Assembling stable hair cell tip link complex via multidentate interactions between harmonin and cadherin 23. Pan L, Yan J, Wu L, Zhang M; Proc Natl Acad Sci U S A. 2009;106:5575-5580. PMID:19297620

2: The structure of the harmonin/sans complex reveals an unexpected interaction mode of the two Usher syndrome proteins. Yan J, Pan L, Chen X, Wu L, Zhang M; Proc Natl Acad Sci U S A. 2010;107:4040-4045. PMID:20142502

3: Mechanistic Basis of Organization of the Harmonin/USH1C-Mediated Brush Border Microvilli Tip-Link Complex. Li J, He Y, Lu Q, Zhang M; Dev Cell. 2016;36:179-189. PMID:26812017