Myosin tails and single α-helical domains

Abstract

The human genome contains 39 myosin genes, divided up into 12 different classes. The structure, cellular function, and biochemical properties of many of these isoforms remains poorly characterized and there is still some controversy as to whether some myosin isoforms are monomers or dimers. Myosin isoforms 6 and 10 contain a stable single α-helical (SAH) domain, situated just after the canonical lever. The SAH domain is stiff enough to be able to lengthen the lever allowing the myosin to take a larger step. In addition, atomic force microscopy and atomistic simulations show that SAH domains unfold at relatively low forces and have a high propensity to refold. These properties are likely to be important for protein function, enabling motors to carry cargo in dense actin networks, and other proteins to remain attached to binding partners in the crowded cell.

Distribution and evolution of stable single α-helices (SAH domains) in myosin motor proteins

“…The importance of the SAH-domains as functional modules providing stiffness and modulating length of the lever in myosins has already been discussed in detail [16,20,21,23,34–36]. Our data show that the presence of SAH-domains in myosins is not myosin class-dependent but the result of a complex history of taxon- and species-specific gain and loss events.…”

“…The monomeric nature of the Drosophila Myo7A myosin in vitro [41,42] and the accumulation of charged residues in the region subsequent to the IQ motifs suggested this region also representing a SAH-domain [36]. However, we only observed veritable SAH-domains in cnidarian and placozoan class-7 myosins, and the short putative SAH-domains in Drosophila Myo7B myosins represent twilight cases (S1 Table, S4 and S5 Figs).…”

The Inner Centromere Protein (INCENP) Coil Is a Single α-Helix (SAH) Domain That Binds Directly to Microtubules and Is Important for Chromosome Passenger Complex (CPC) Localization and Function in Mitosis

“…Here we show that the central region of INCENP is not a coiled coil but instead is a single α-helix (SAH) domain similar to that found in myosin 10 and many other proteins ( 18 – 21 ). The N-terminal portion of this SAH is capable of binding directly to microtubules.…”

Gastrophysical and chemical characterization of structural changes in cooked squid mantle

“…Further, it is seen that α‐helices are present at 1650, 1260–1300, and 890–945 cm −1 , which are characteristic for collagen and have previously been used to track structural changes of collagen from α‐helix to random coil during heating of burnt skin (Ye et al., 2019). Nonetheless, myosin also contains α‐helixes (Batchelor et al., 2015) as well as other protein structures. Consequently, the different events displayed by RS of squid meat are as opposed to purified samples difficult to ascribe to specific proteins, based on the included sample treatments for RS.…”