Molecular mechanism of actomyosin-based motility

Geeves, Michael A.; Fedorov, Roman; Manstein, Dietmar J.

doi:10.1007/s00018-005-5015-5

Cited by 91 publications

(94 citation statements)

References 123 publications

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“…The blocked head is shown in yellow with the amino acids framing loop 2 shown in magenta, although the actual residues of loop 2 are missing. The remaining residues of the approximate actin-binding interface have been colored in dark green (37). (Inset) Magnification of the interaction after a clockwise 90°rotation around the coiled-coil main axis.…”

Section: Methodsmentioning

confidence: 99%

Crystal structures of human cardiac β-myosin II S2-Δ provide insight into the functional role of the S2 subfragment

Blankenfeldt

Thomä

Wray

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

101

132

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Myosin II is the major component of the muscle thick filament. It consists of two N-terminal S1 subfragments (''heads'') connected to a long dimeric coiled-coil rod. The rod is in itself twofold symmetric, but in the filament, the two heads point away from the filament surface and are therefore not equivalent. This breaking of symmetry requires the initial section of the rod, subfragment 2 (S2), to be relatively flexible. S2 is an important functional element, involved in various mechanisms by which the activity of smooth and striated muscle is regulated. We have determined crystal structures of the 126 N-terminal residues of S2 from human cardiac ␤-myosin II (S2-⌬), of both WT and the disease-associated E924K mutant. S2-⌬ is a straight parallel dimeric coiled coil, but the N terminus of one chain is disordered in WT-S2-⌬ due to crystal contacts, indicative of unstable local structure. Bulky noncanonical side chains pack into a͞d positions of S2-⌬'s N terminus, leading to defined local asymmetry and axial stagger, which could induce nonequivalence of the S1 subfragments. Additionally, S2 possesses a conserved charge distribution with three prominent rings of negative potential within S2-⌬, the first of which may provide a binding interface for the ''blocked head'' of smooth muscle myosin in the OFF state. The observation that many disease-associated mutations affect the second negatively charged ring further suggests that charge interactions play an important role in regulation of cardiac muscle activity through myosin-binding protein C.coiled coil ͉ muscle ͉ crystallography ͉ regulation ͉ familial hypertrophic cardiomyopathy M uscle contraction results from the ATP-dependent cyclic interaction of the proteins myosin II and actin, assembled in thick and thin filaments, respectively. Myosin II consists of two heavy chains, each of which binds one essential and one regulatory light chain (Fig.

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Section: Methodsmentioning

confidence: 99%

Crystal structures of human cardiac β-myosin II S2-Δ provide insight into the functional role of the S2 subfragment

Blankenfeldt

Thomä

Wray

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

101

132

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“…In the weakly bound transition state, when a leading head is searching for a new binding site on actin to continue forward motion, loop 2 maintains contact with actin and appears to act as a tether (16) (Fig. 1).Increasing the net positive charge of loop 2 increases the affinity of myosin for actin (14,(17)(18)(19). We previously showed that replacing loop 2 of mouse myosin V (net loop charge of ϩ5) with the corresponding loop from a yeast class V myosin (Myo4p, net loop charge of 0) caused a dramatic reduction in processive run lengths, especially at high ionic strength (20).…”

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confidence: 99%

Engineering the Processive Run Length of Myosin V

Hodges

Krementsova

Trybus

2007

Journal of Biological Chemistry

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The processive motor myosin V has a high affinity for actin in the weak binding states when compared with non-processive myosins. Here we test whether this feature is essential for myosin V to walk processively along an actin filament. The net charge of loop 2, a surface loop implicated in the initial weak binding between myosin and actin, was increased or decreased to correspondingly change the affinity of myosin V for actin in the weak binding state, without changing the velocity of movement. Processive run lengths of single molecules were determined by total internal reflection fluorescence microscopy. Reducing the net positive charge of loop 2 significantly decreased both the affinity of myosin V for actin and the processive run length. Conversely, the addition of positive charge to loop 2 increased actin affinity and processive run length. We hypothesize that a high affinity for actin allows the detached head of a stepping myosin V to find its next actin binding site more quickly, thus decreasing the probability of run termination.Myosin Va is a processive actin-based motor protein involved in intracellular cargo transport and membrane trafficking (1). It takes 36-nm steps along an actin filament in a hand-over-hand fashion, with the trailing and leading heads swapping position during each step (2, 3). Myosin V has both structural and kinetic adaptations that allow it to be an efficient processive motor (4 -6). The rate-limiting step for myosin V is ADP release, ensuring that it spends most of its time strongly bound to actin (7). In contrast, the rate-limiting step for low duty cycle, non-processive class II myosins is phosphate release, and thus these motors spend the majority of their ATPase cycle detached from actin in a weak binding state. The long (ϳ24 nm) lever arm allows myosin V to take 36-nm steps, equal to the semi-repeat of actin (8), and to generate intramolecular strain that helps gate nucleotide release from the leading and the trailing heads (9 -12). Loop 2, a surface loop implicated in the initial weak electrostatic interaction with actin, is longer and more positively charged in myosin V than in class II myosins, resulting in a higher affinity for actin in the presence of MgATP (13,14). Loop 2 is disordered in the myosin V crystal structure (Protein Data Bank code 1oeq) (15), whereas it adopts an ordered structure when bound to actin (16). The position of loop 2 in various nucleotide states was identified from discrepancy mapping, a technique that identifies regions of the three-dimensional electron microscopy reconstruction that have more density than can be accounted for by the docked atomic models. By these methods, loop 2 was shown to undergo significant rearrangements in different nucleotide states (16). In the weakly bound transition state, when a leading head is searching for a new binding site on actin to continue forward motion, loop 2 maintains contact with actin and appears to act as a tether (16) (Fig. 1).Increasing the net positive charge of loop 2 increases the affinity of my...

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“…2) that lies inside one of the ATP-binding site to the actin molecule, found at the subdomain 3. This amino acid substitution can influence the actin's affinity for ATP, a feature that has been described in actin isoforms of some vertebrate species, including fish, and in Sacharomyces cervisae, a yeast that has one essential actin gene that encodes a protein that shares a high identity degree (87%) to vertebrate skeletal muscle actins (Geeves et al 2005, Mercer et al 2011. Similarly, it has been evidenced that a Ser/Ala substitution at the amino acid 14, at the actin subdomain 1, results in a 40 to 60-fold decrease in actin's affinity for ATP (Chen et al 1995), since Alanine has a lower hydrogen bonding capacity.…”

Section: Discussionmentioning

confidence: 99%

Characterization of α-actin isoforms in white and red skeletal muscle types of Leporinus macrocephalus (Characiformes, Anostomidae)

Alves-Costa

Silva

Wasko

2015

An. Acad. Bras. Ciênc.

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Two α-actin genes of the fish Leporinus macrocephalus, referring to white and red muscle tissues, were isolated. Actin isoforms, that mainly differed by a Ser/Ala 155 substitution, can have a functional significance related to actin-ATP interaction. An Ala 155 residue, as observed in the α-skeletal actin from red muscle, results in a decrease in actin's affinity for ATP, which may also be associated to the slow contractile performance of this tissue. Furthermore, a Phe/Ile 262 substitution at the red muscle actin leads to a hydrophobicity variation at the D-plug of the protein, which could alter its stability. Data on qRT-PCR evidenced a significant higher actin mRNA level in white muscle when compared to red muscle (T=105 Mann Whitney; p<0.001). This finding could be related to the energetic demands of the white muscle tissue, with fast contraction fibers and glycolytic metabolism for energy supply. Available data on muscle actins lead to the proposal that white and red α-skeletal actins are genetically and functionally distinguishable in fish species, a feature that is not found in other vertebrate groups.

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Molecular mechanism of actomyosin-based motility

Cited by 91 publications

References 123 publications

Crystal structures of human cardiac β-myosin II S2-Δ provide insight into the functional role of the S2 subfragment

Crystal structures of human cardiac β-myosin II S2-Δ provide insight into the functional role of the S2 subfragment

Engineering the Processive Run Length of Myosin V

Characterization of α-actin isoforms in white and red skeletal muscle types of Leporinus macrocephalus (Characiformes, Anostomidae)

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