CryoEM Structure of<i>Drosophila</i>Flight Muscle Thick Filaments at 7Å Resolution

Daneshparvar, Nadia; Taylor, David; O’Leary, Thomas S.; Rahmani, Hamidreza; Yeganeh, Fatemeh Abbasi; Previs, Michael J.; Taylor, Kenneth A.

doi:10.1101/2020.06.05.136580

Cited by 4 publications

(19 citation statements)

References 64 publications

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“…It is tilted slightly toward the bare zone. The position is essentially identical to that found in Drosophila [13]. The small stub of the proximal S2 points directly at the inner edge of the floating density (Figure 3C,D).…”

Section: Myosin Headssupporting

confidence: 76%

“…The reconstruction has no density that resembles either individual myosin heads or the IHM. Apparently, the myosin heads are disordered in relaxed Bombus thick filaments similar to how they are in relaxed Drosophila flight muscle thick filaments [13]. When the reconstruction is low-pass filtered to 15 Å, a pancake-shaped floating density is observed, centered at the same radius and axial position of the ordered heads of relaxed Lethocerus flight muscle thick filaments but much smaller than the expected volume of an individual myosin head (Figure 3A,B).…”

Section: Myosin Headsmentioning

confidence: 69%

“…The Skip 1 accommodation region in Bombus is significantly less angled relative to the filament axis than in Lethocerus. Where the proximal S2 enters the filament backbone, more of the S2 is visible in Bombus than was seen in Drosophila [13]. Compared with Lethocerus, where the proximal S2 is angled with respect to the filament axis stabilized by the Free Head binding the filament backbone, the stub of S2 seen in both Drosophila and Bombus, is parallel with the initial S2 segment as it enters the filament backbone.…”

Section: Coiled Coils and Skip Residuesmentioning

confidence: 95%

“…The Bombus thick filament backbone has many features in common with the backbones of both Drosophila and Lethocerus. Myosin tails of Bombus are contained within an annulus with an outer diameter of ~190 Å and an inner diameter of ~80 Å, which is similar to Lethocerus [8] but slightly larger than Drosophila [13]. Of the initial references tried, the low pass filtered Lethocerus map generated a better reconstruction than using the Drosophila map or starting from a structure-free reference.…”

Section: Myosin Tail Structure and Arrangementmentioning

confidence: 99%

“…The relaxed thick filament reconstructions from Drosophila melanogaster failed to show any ordered myosin heads [13,14] leaving open the question of whether this particular muscle forms an IHM that is itself disordered, because it fails to attach to the filament backbone, or whether the motif forms at all. Supporting the former was the presence of non-myosin proteins decorating the filament backbone in such a way that they could provide a steric block to the binding of myosin heads.…”

Section: Introductionmentioning

confidence: 99%

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Structure of the Flight Muscle Thick Filament from the Bumble Bee, Bombus ignitus, at 6 Å Resolution

Rahmani

Yeganeh

et al. 2022

IJMS

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Four insect orders have flight muscles that are both asynchronous and indirect; they are asynchronous in that the wingbeat frequency is decoupled from the frequency of nervous stimulation and indirect in that the muscles attach to the thoracic exoskeleton instead of directly to the wing. Flight muscle thick filaments from two orders, Hemiptera and Diptera, have been imaged at a subnanometer resolution, both of which revealed a myosin tail arrangement referred to as “curved molecular crystalline layers”. Here, we report a thick filament structure from the indirect flight muscles of a third insect order, Hymenoptera, the Asian bumble bee Bombus ignitus. The myosin tails are in general agreement with previous determinations from Lethocerus indicus and Drosophila melanogaster. The Skip 2 region has the same unusual structure as found in Lethocerus indicus thick filaments, an α-helix discontinuity is also seen at Skip 4, but the orientation of the Skip 1 region on the surface of the backbone is less angled with respect to the filament axis than in the other two species. The heads are disordered as in Drosophila, but we observe no non-myosin proteins on the backbone surface that might prohibit the ordering of myosin heads onto the thick filament backbone. There are strong structural similarities among the three species in their non-myosin proteins within the backbone that suggest how one previously unassigned density in Lethocerus might be assigned. Overall, the structure conforms to the previously observed pattern of high similarity in the myosin tail arrangement, but differences in the non-myosin proteins.

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Section: Myosin Headssupporting

confidence: 76%

Section: Myosin Headsmentioning

confidence: 69%

Section: Coiled Coils and Skip Residuesmentioning

confidence: 95%

Section: Myosin Tail Structure and Arrangementmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Structure of the Flight Muscle Thick Filament from the Bumble Bee, Bombus ignitus, at 6 Å Resolution

Rahmani

Yeganeh

et al. 2022

IJMS

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Nanobodies combined with DNA-PAINT super-resolution reveal a staggered titin nano-architecture in flight muscles

Schnorrer

Schueder

Mangeol

et al. 2022

Preprint

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Sarcomeres are the force producing units of all striated muscles. Their nanoarchitecture critically depends on the large titin protein, which in vertebrates spans from the sarcomeric Z-disc to the M-band and hence links actin and myosin filaments stably together. This ensures sarcomeric integrity and determines the length of vertebrate sarcomeres. However, the instructive role of titins for sarcomeric architecture outside of vertebrates is not as well understood. Here, we used a series of nanobodies, the Drosophila titin nanobody toolbox, recognising specific domains of the two Drosophila titin homologs Sallimus and Projectin to determine their precise location in intact flight muscles. By combining nanobodies with DNA-PAINT super-resolution microscopy, we found that, similar to vertebrate titin, Sallimus bridges across the flight muscle I-band, whereas Projectin is located at the beginning of the A-band. Interestingly, the ends of both proteins overlap at the I-band/A-band border, revealing a staggered organisation of the two Drosophila titin homologs. This architecture may help to stably anchor Sallimus at the myosin filament and hence ensure efficient force transduction during flight.

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In situ structures from relaxed cardiac myofibrils reveal the organization of the muscle thick filament

Tamborrini

Wang

Wagner

et al. 2023

Preprint

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The thick filament is a key component of sarcomeres, the basic force-generating and load-bearing unit of striated muscle. Mutations in thick filament proteins are associated with familial hypertrophic cardiomyopathy and other heart and muscle diseases. Despite this central importance for sarcomere force generation, it remains unclear how thick filaments are structurally organized and how its components interact with each other and with thin filaments to enable highly regulated muscle contraction. Here, we present the molecular architecture of native cardiac sarcomeres in the relaxed state, determined by electron cryo-tomography. Our reconstruction of the thick filament reveals the three-dimensional organization of myosin heads and tails, myosin-binding protein C (MyBP-C) and titin, elucidating the structural basis for their interaction during muscle contraction. The arrangement of myosin heads is variable depending on their position along the filament, suggesting that they have different capacities in terms of strain susceptibility and activation. Myosin tails exhibit a distinct arrangement and pattern of interactions. These are likely orchestrated by three alpha and three beta titin chains that are arranged like a spring, suggesting the existence of specialized roles of thick filament segments in length-dependent activation and contraction. Surprisingly, while the three titin alpha chains run along the entire length of the thick filament, titin beta does not. The structure also demonstrates that the C-terminal region of MyBP-C binds myosin tails and unexpectedly also directly interacts with the myosin heads, suggesting a previously undescribed direct role in the preservation of the myosin OFF state. Furthermore, we visualize how MyBP-C forms links between thin and thick filaments. These findings establish a robust groundwork for forthcoming research endeavors aiming to explore muscle disorders that involve sarcomeric structural components.

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CryoEM Structure ofDrosophilaFlight Muscle Thick Filaments at 7Å Resolution

Cited by 4 publications

References 64 publications

Structure of the Flight Muscle Thick Filament from the Bumble Bee, Bombus ignitus, at 6 Å Resolution

Structure of the Flight Muscle Thick Filament from the Bumble Bee, Bombus ignitus, at 6 Å Resolution

Nanobodies combined with DNA-PAINT super-resolution reveal a staggered titin nano-architecture in flight muscles

In situ structures from relaxed cardiac myofibrils reveal the organization of the muscle thick filament

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