Myosin binding of N-terminal truncation and deletion mutants. (A) SDS-PAGE (8–22%) of chicken and rat constructs expressed in the coupled transcription/translation system. Lanes 1–6, chicken mutants: lane 1, cMy1; lane 2, cMy2; lane 3, cMy3; lane 4, cMy2–3; lane 5, cMy1 + 3; lane 6, cMy1–3. Lanes 7–12, rat mutants: lane 7, rMy1; lane 8, rMy2; lane 9, rMy3; lane 10, rMy2–3; lane 11, rMy1 + 3; lane 12, rMy1–3. Lane 13, luciferase. Molecular weight standards are in kilodaltons. All constructs express proteins of the expected size, although in the case of longer constructs, additional lower bands representing either alternative initiation events or proteolytic degradation products can be observed. (B) Solid-phase binding assay of chicken and rat constructs. The rows are labeled after the domain nomenclature used in Figure 1. a, Chicken constructs; b, rat constructs; c, luciferase control. Different amounts of LMM fragment were used: 1 μg LMM fragment (columns 1, 3, 5) and 100 ng LMM fragment (columns 2, 4, 6).