Tropomyosin-binding properties of the CHASM protein are dependent upon its calponin homology domain

Abstract

The calponin homology-associated smooth muscle protein (CHASM) can modulate muscle contractility, and its biological action may involve an interaction with the contractile filament. In this study, we demonstrate an interaction between CHASM and tropomyosin. Deletion constructs of CHASM were generated, and pull-down assays revealed a minimal deletion construct that could bind tropomyosin. Removal of the calponin homology (CH) domain or expression of the CH domain alone did not enable binding. The interaction was characterized by microcalorimetry with a dissociation constant of 2.0 × 10 −6 M. Confocal fluorescence microscopy also showed green fluorescent protein (GFP)–CHASM localization to filamentous structures within smooth muscle cells, and this targeting was dependent upon the CH domain. Structured summary MINT- 7966126: CHASM (uniprotkb: Q99LM3), Tropomyosin alpha (uniprotkb: P04268) and Tropomyosin beta (uniprotkb: P19352) physically interact (MI: 0915) by isothermal titration calorimetry (MI: 0065) MINT- 7966073: CHASM (uniprotkb: Q99LM3) physically interacts (MI: 0914) with Tropomyosin beta (uniprotkb: P58776) and Tropomyosin alpha (uniprotkb: P58772) by pull down (MI: 0096) MINT- 7966187: Tropomyosin alpha (uniprotkb: P04268) and Tropomyosin beta (uniprotkb: P19352) physically interact (MI: 0915) with CHASM (uniprotkb: Q99LM3) by pull down (MI: 0096) MINT- 7966090: CHASM (uniprotkb: Q99LM3) binds (MI: 0407) to Tropomyosin alpha (uniprotkb: P04268) by pull down (MI: 0096)