This domain can be found in the myosin-binding motif (m-domain) region present in myosin-binding protein C (MyBP-C). MyBP-C is a sarcomeric assembly protein necessary for the regulation of sarcomere structure and function [1]. The MyBP-C family of proteins consists mainly of modules with immunoglobulin (Ig) or fibronectin folds [2]. This domain exhibits a three-helix bundle fold and there is a known actin-binding motif, LK(R/K)XK positioned in the third helix (alpha3), similar to that found in villin and related proteins [1].

1: Structural insight into unique cardiac myosin-binding protein-C motif: a partially folded domain. Howarth JW, Ramisetti S, Nolan K, Sadayappan S, Rosevear PR; J Biol Chem. 2012;287:8254-8262. PMID:22235120

2: A Highly Conserved Yet Flexible Linker Is Part of a Polymorphic Protein-Binding Domain in Myosin-Binding Protein C. Michie KA, Kwan AH, Tung CS, Guss JM, Trewhella J; Structure. 2016;24:2000-2007. PMID:27720588