Affinage

MYBPC1

Myosin-binding protein C, slow-type · UniProt Q00872

Length
1141 aa
Mass
128.3 kDa
Annotated
2026-04-29
16 papers in source corpus 7 papers cited in narrative 7 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

MYBPC1 encodes slow skeletal myosin-binding protein C (sMyBP-C), a sarcomeric A-band protein that regulates actomyosin cross-bridge cycling and maintains sarcomere structural integrity in slow-twitch skeletal muscle. Its N-terminal M-motif dynamically binds myosin to modulate contraction, while its C-terminal domains scaffold muscle-type creatine kinase (MM-CK) onto myosin, coupling local ATP regeneration to consumption and reducing the apparent Km of myosin ATPase activity (PMID:21426302). The protein undergoes extensive alternative splicing and PKA/PKC-mediated phosphorylation that tune its regulatory functions across muscle fiber types (PMID:27683561). Pathogenic M-motif variants that either increase or decrease myosin binding cause sarcomeric disorganization, membrane misregister, reduced contractile force, and tremor in mouse and zebrafish models, establishing MYBPC1 mutations as a cause of congenital myopathy with tremor (PMID:23873045, PMID:34437302).

Mechanistic history

Synthesis pass · year-by-year structured walk · 6 steps
  1. 2011 High

    The discovery that sMyBP-C physically recruits MM-CK to myosin via its C-terminal domains established MYBPC1 as a metabolic adaptor in the sarcomere, answering how ATP supply is spatially coupled to cross-bridge cycling.

    Evidence Co-immunoprecipitation, domain-mapping pulldowns, and reconstituted in vitro ATPase assays showing reduced Km of myosin when MM-CK is tethered via sMyBP-C

    PMID:21426302

    Open questions at the time
    • Whether the MM-CK–sMyBP-C interaction is physiologically regulated in vivo remains untested
    • No structural model of the ternary complex exists
    • Contribution of this scaffolding function to contractile force in intact muscle is unknown
  2. 2013 High

    Loss-of-function studies in zebrafish demonstrated that MYBPC1 is essential for slow muscle myofibril assembly and embryonic motor activity, establishing a non-redundant structural and functional role in vivo.

    Evidence Morpholino knockdown in zebrafish with electron microscopy of sarcomeres and behavioral motor assays; dominant-negative effects of human W236R and Y856H variants confirmed by mRNA injection

    PMID:23873045

    Open questions at the time
    • Morpholino approach does not exclude off-target effects despite mutation rescue
    • Whether the phenotype is cell-autonomous to slow muscle fibers was not resolved
    • No mammalian loss-of-function model was available at this stage
  3. 2016 Medium

    Documentation of extensive exon shuffling and PKA/PKC phosphorylation of sMyBP-C variants revealed a post-translational regulatory layer, suggesting that MYBPC1's function is tunable across fiber types and contractile states.

    Evidence RT-PCR exon analysis and kinase phosphorylation assays (review of published biochemical data)

    PMID:27683561

    Open questions at the time
    • Functional consequences of individual splice variants on cross-bridge kinetics are uncharacterized
    • Phosphorylation sites have not been linked to specific physiological stimuli in vivo
    • Review-level synthesis without new primary data
  4. 2019 Medium

    Biochemical characterization of M-motif disease variants showed that mutations can either increase (Y247H, E248K) or decrease (L263R) myosin binding, defining a bidirectional mechanism by which MYBPC1 variants perturb cross-bridge regulation.

    Evidence In vitro binding and kinetic assays comparing wild-type and mutant N-terminal fragments for myosin interaction

    PMID:31025394 PMID:31264822

    Open questions at the time
    • Effects on actin thin-filament interactions were not assessed
    • No single-molecule or motility assays to confirm kinetic predictions
    • Structural basis of altered binding relies partly on modeling rather than experimental structures
  5. 2021 High

    A CRISPR knock-in mouse carrying E248K recapitulated myopathy and tremor, with ultrastructural analysis revealing sarcomeric disorganization and membrane misregister as the primary pathological mechanism, confirming that an M-motif gain-of-binding variant causes disease through structural disruption.

    Evidence E248K knock-in mouse with electron microscopy, ex vivo contractile force measurements, and behavioral phenotyping

    PMID:34437302

    Open questions at the time
    • Whether increased myosin binding directly causes structural disorganization or acts indirectly is unresolved
    • Contribution of heterozygous vs. homozygous state to phenotype severity not fully delineated
    • No therapeutic rescue attempted
  6. 2025 Medium

    Longitudinal analysis of the E248K mouse revealed muscle-type-specific and age/sex-dependent contractile deficits that track with sarcomere disorganization, reinforcing a primarily structural role for sMyBP-C and exposing selective vulnerability of slow-twitch fibers.

    Evidence Quantitative sarcomere analysis and contractility measurements across soleus, gastrocnemius, and TA muscles at multiple ages and in both sexes

    PMID:40569690

    Open questions at the time
    • Molecular basis of sex-specific differences is unknown
    • Whether compensatory mechanisms protect fast-twitch fibers has not been investigated
    • Single-lab, single-model findings

Open questions

Synthesis pass · forward-looking unresolved questions
  • How the N-terminal M-motif interaction with myosin is structurally coordinated with C-terminal scaffolding of MM-CK, and how phosphorylation and splicing integrate to tune cross-bridge cycling in vivo, remain central unresolved questions.
  • No high-resolution structure of sMyBP-C bound to myosin
  • Phosphorylation-dependent regulation has not been tested in the knock-in mouse
  • In vivo functional consequences of individual splice variants are entirely unknown

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0005198 structural molecule activity 3 GO:0008092 cytoskeletal protein binding 3 GO:0060090 molecular adaptor activity 1
Localization
GO:0005856 cytoskeleton 4
Pathway
R-HSA-397014 Muscle contraction 3
Partners
CKMMYH7

Evidence

Reading pass · 7 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2011 sMyBP-C (MYBPC1) physically interacts with muscle-type creatine kinase (MM-CK) via its C-terminal domains, which are also the myosin-binding domains. This interaction is creatine-concentration dependent and pH-sensitive (favoring acidic conditions, dissociating above pH 7.5). MYBPC1 acts as an adaptor linking myosin (ATP consumer) and MM-CK (ATP regenerator), reducing the apparent Km of myosin in ATPase activity assays when all three proteins are associated. Co-immunoprecipitation, domain-mapping pulldown experiments, in vitro ATPase activity assay The Biochemical journal High 21426302
2013 mybpc1 is required for embryonic motor activity and slow skeletal muscle myofibril organization in zebrafish; morpholino knockdown causes severe body curvature, reduced sarcomere numbers in slow muscle, cardiac edema, and impaired motor activity. Human disease mutations W236R and Y856H act as dominant negatives when expressed as mRNA in zebrafish, causing decreased motor activity and survival. Antisense morpholino knockdown in zebrafish, mRNA injection of human disease mutants, electron microscopy of sarcomere structure, behavioral motor assays Human molecular genetics High 23873045
2019 The M-motif of sMyBP-C (MYBPC1) dynamically interacts with myosin; mutations Y247H and E248K in the NH2-terminal M-motif markedly increase binding of the NH2-terminus to myosin, likely interfering with normal actomyosin cross-bridge cycling and acting as a mechanistic basis for myogenic tremor. In vitro biochemical binding assays, molecular modeling Annals of neurology Medium 31025394
2019 The M-motif variant p.Leu263Arg in MYBPC1 results in decreased binding of the M-motif to myosin in vitro, impairing formation of actomyosin cross-bridges during muscle contraction; variant p.Leu259Pro alters M-motif structure per protein modeling. In vitro biochemical and kinetic binding assays, protein modeling Human mutation Medium 31264822
2021 The MYBPC1 E248K knock-in mouse model recapitulates myopathy and tremor; at the sarcomeric level, mutant muscles show disordered and misaligned sarcomeres with fragmented and out-of-register internal membranes, resulting in reduced force production and tremor initiation, establishing that the E248K variant drives a loss-of-function phenotype through sarcomeric disorganization. Knock-in mouse model generation (CRISPR), biochemical assays, electron microscopy/ultrastructural analysis, in vitro and ex vivo contractile force measurements, behavioral/phenotypic assessments JCI insight High 34437302
2016 MYBPC1 undergoes extensive exon shuffling producing multiple slow skeletal muscle splice variants, which are co-expressed in different combinations in slow and fast skeletal muscles. The sMyBP-C variants are subjected to PKA- and PKC-mediated phosphorylation at both constitutive and alternatively spliced sites, modulating their regulatory roles. RT-PCR/exon analysis, kinase phosphorylation assays (implied review of published biochemical data) Frontiers in physiology Medium 27683561
2025 Using the E248K knock-in mouse, contractile impairment in soleus (but not gastrocnemius) and age/sex-specific TA dysfunction were observed; quantitative sarcomere analysis showed structural deficits coinciding with contractile dysfunction, supporting a primarily structural role for sMyBP-C in skeletal muscle. Knock-in mouse muscle contractility measurements, quantitative sarcomere organization analysis, aging time-course experiments across muscle types and sexes JCI insight Medium 40569690

Source papers

Stage 0 corpus · 16 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2013 MYBPC1 mutations impair skeletal muscle function in zebrafish models of arthrogryposis. Human molecular genetics 52 23873045
2012 Autosomal recessive lethal congenital contractural syndrome type 4 (LCCS4) caused by a mutation in MYBPC1. Human mutation 46 22610851
2011 Slow skeletal muscle myosin-binding protein-C (MyBPC1) mediates recruitment of muscle-type creatine kinase (CK) to myosin. The Biochemical journal 41 21426302
2019 Novel mutations in MYBPC1 are associated with myogenic tremor and mild myopathy. Annals of neurology 38 31025394
2016 MYBPC1, an Emerging Myopathic Gene: What We Know and What We Need to Learn. Frontiers in physiology 34 27683561
2019 Heterozygous variants in MYBPC1 are associated with an expanded neuromuscular phenotype beyond arthrogryposis. Human mutation 25 31264822
2011 MYBPC1 computational phosphoprotein network construction and analysis between frontal cortex of HIV encephalitis (HIVE) and HIVE-control patients. Cellular and molecular neurobiology 19 21061152
2021 Sarcomeric deficits underlie MYBPC1-associated myopathy with myogenic tremor. JCI insight 15 34437302
2016 Expanding the MYBPC1 phenotypic spectrum: a novel homozygous mutation causes arthrogryposis multiplex congenita. Clinical genetics 13 26661508
2023 A Case Series of Patients With MYBPC1 Gene Variants Featuring Undulating Tongue Movements as Myogenic Tremor. Pediatric neurology 9 37392669
2024 Congenital tremor and myopathy secondary to novel MYBPC1 variant. Journal of the neurological sciences 8 38185014
2021 Effect of growth selection of broilers on breast muscle satellite cell function: Response of satellite cells to NOV, COMP, MYBP-C1, and CSRP3. Comparative biochemistry and physiology. Part A, Molecular & integrative physiology 5 33548540
2024 Compound heterozygous variants in MYBPC1 lead to severe distal arthrogryposis type-1 manifestations. Gene 4 38438057
2022 MYBPC1 is a key regulator for laryngeal carcinoma formation. Anti-cancer drugs 3 36539363
2024 Expanding the Spectrum of Congenital Myopathy Linked to Variants in the MYBPC1 Gene: A Clinical Report. Neurology. Clinical practice 2 38690148
2025 Sex-dependent and muscle-specific progression of the MYBPC1 E248K Myotrem myopathy in response to aging. JCI insight 0 40569690