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. 2017 Dec 19;6:e32742. doi: 10.7554/eLife.32742

Figure 3. Interdomain connectivity at the converter/Nter/lever junction.

(A) Interaction profile of R788 in the pre-powerstroke state. R788 is shown in orange colored sticks and the converter is colored in white, the relay helix in red, the SH1-SH2 helix in purple, and the lever arm in green colored cartoon representation. The inset shows a close-up view of the complete R788 interaction profile and is rotated 137° respective to the main panel. The guanidinium group of R788 forms hydrogen bonds (2.8 Å) with backbone oxygen atom of Q730 from the SH1 helix and the backbone oxygen atom of G731 (3.0 Å) of the converter. The δ-nitrogen atom of R788 interacts (3.0 Å) with N776 backbone oxygen atom of N776. The R788 guanidinium group interacts (3.1 Å) with the hydroxyl group of N776 of the converter. The backbone nitrogen atom of R788 interacts (3.1 Å) with the carbonyl group of L777 of the converter. The backbone carbonyl group of R788 interacts (3.4 Å) with the backbone nitrogen of V791 of the lever as well as a water molecule (3.0 Å). The hydroxyl group from relay helix Y518 interacts with the backbone nitrogen atom of G731 (2.8 Å) and backbone oxygen atom of F732 (3.4 Å). F732 forms hydrophobic interactions with the methylene groups of R788 with the latter positioned in van der Waals distance to relay loop W525. All the amino acids involved in interactions with R788 are shown as sticks and water molecules as spheres. (B) Sequence alignment of selected regions from relay helix, SH1 helix, converter and lever arm shows the high sequence conservation within the myosin-2 motor domain. The asterisk indicates the invariant, positively charged residue corresponding to NM2C R788. The interactions of NM2C R788 with structural elements of the L50 kDa, the converter, and the lever are highlighted. Abbreviations used: Hs NM2C: human NM2C (NP_079005.3); Hs NM2A: human nonmuscle myosin-2A (NP_002464.1); NM2B: human nonmuscle myosin-2B (NP_005955.3); Gg SM: chicken smooth muscle myosin-2 (NP_990605.2); Hs CARD: human beta β-cardiac muscle myosin-2 (NP_000248.2); Ai ST: scallop striated muscle myosin-2 (P24733.1). PDB entries are indicated when available. Lysine residues that replace R788 in cardiac and striated muscle myosins-2 highlighted in the boxed area.

Figure 3.

Figure 3—figure supplement 1. Interdomain connectivity at the converter/Nter/lever junction in muscle myosins-2.

Figure 3—figure supplement 1.

In contrast to NM2C (Figure 3), the substitution of R788 with K763 in scallop striated muscle myosin-2 (PDB entry IQVI) (A) and K766 in human β-cardiac muscle myosin-2 (PDB entry 4DB1) (B) reduces the number of side chain and main chain interactions at the converter/Nter/lever junction. (C) In the conservative mutant R788K, the side chain: side chain and side chain: main chain interactions are reduced compared to NM2C (Figure 3). A further reduction in side chain: side chain and side chain: main chain interactions is achieved in the charge reversal mutant R788E (D). Coloring is according to Figure 3.