GDF-8 / Myostatin (mature recombinant protein)

1 Identity

Recombinant secreted TGF-beta superfamily ligand — disulfide-linked homodimer of the mature signaling domain, cystine-knot fold. Not a peptide and not a synthetic article. UniProt MSTN O14793. Distinct from Myostatin Propeptide, the N-terminal prodomain, which this catalog carries as a separate record. Routinely conflated with GDF-11 (BMP-11, UniProt O95390).

Sequence

No defined synthetic sequence. Myostatin is synthesized as a precursor with an N-terminal prodomain, secreted as a latent complex, and activated by proteolysis — latent myostatin is activated by the BMP-1/tolloid family of metalloproteinases (PMID 14671324). The article carried here is the mature signaling domain, released from the precursor by that processing, which assembles as a disulfide-linked homodimer with the cystine-knot fold characteristic of the superfamily. Exact residue numbering, construct boundary, cysteine count, intrachain and interchain disulfide connectivity, and any N-terminal Met or affinity tag are fixed against UniProt O14793 and against the supplier's stated construct — not against a datasheet summary, and not against this page, which deliberately does not restate them from memory. No residue string for this article has been independently confirmed, and none is supplied here from recall.

Molecular formula

Not established, and not establishable as a single formula until the construct boundary, the tag state and the dimerization state are declared. Even then a formula would describe a backbone rather than the article, since expression-system variation and refolding fidelity are what distinguish lots. No formula is asserted.

Average mass

Not established, and no single number is printed. What can be said: the mature domain is reported in the low tens of kilodaltons as a homodimer, with the reduced monomer running at roughly half that on SDS-page, and E. Coli-expressed material carries no glycan. Those are gel estimates and a range, not a mass. Three things move the figure independently, and none of them is visible in a trade name: the exact construct boundary; the presence or absence of an N-terminal methionine or an affinity tag; and whether the certificate refers to the reduced monomer or to the disulfide-linked dimer. Any supplier printing a single molecular weight for this article is printing a backbone calculation for one of those states and calling it a mass.

Monoisotopic mass

Not applicable and not measurable. A monoisotopic mass requires an isotopically resolved envelope, which is not obtainable on a disulfide-linked protein dimer of this size by any routine method. Intact-mass work here is deconvoluted average mass, run under both reducing and non-reducing conditions so that the dimer and the monomer are seen separately. Any monoisotopic figure offered for myostatin is fabricated.

Salt / variant note

Multi-molecule name at kilodalton scale, and the principal confusion is with a different gene product. (1) GDF-11 / BMP-11, UniProt O95390 — approximately 90 percent identical to GDF-8 in the mature signaling domain. This is the root of essentially every technical and interpretive problem in the field: most antibodies and immunoassays cannot cleanly distinguish the two, and targeted mass-spectrometry methods were developed specifically to determine absolute levels of GDF8 and GDF11 in serum because conventional assays could not (PMID 32104967). That single technical fact clouds a substantial fraction of the published circulating-GDF11 literature, and it means an antibody-based identity test on a purchased lot is not an identity test: targeted mass spectrometry on signature peptides is the first identity requirement for this article, not an option. (2) LATENT (PRO-form) material against mature-domain material — these behave completely differently in bioassay, and the distinction must be confirmed on the certificate; it is a far more consequential specification than purity percentage. (3) Myostatin Propeptide, the N-terminal prodomain alone at roughly 240 residues, carried as a separate record here. (4) Reduced monomer against disulfide-linked homodimer, which differ by a factor of two in apparent mass on a gel. (5) Expression system — E. Coli refold, CHO, HEK, Sf21 — all shipping under one name, with the E. Coli article carrying no glycan and unverifiable disulfide fidelity. (6) Tagged and Fc-fusion constructs, which move the mass by tens of kilodaltons.

2 Class & testing panel

Form

Single article

Testing panel

P4 — panel definition

3 Primary sources & evidence

The index reports the design and provenance of the literature, not a conclusion about effect.

The literature underlying the GDF-8 and GDF-11 pair is unusually strong for an article of this kind, and its strength attaches to the underlying biology rather than to any product. Study types and identifiers only. Mouse genetics: McPherron, Lawler and Lee, Nature 1997, PMID 9139826. Cattle genetics: PNAS 1997, PMID 9356471. Human case report, n=1: Schuelke and colleagues, N Engl J Med 2004, PMID 15215484. Mouse: Science 2002, PMID 12029139; PMID 12447939; PMID 10962344; PMID 12060865; PMID 11877467; PMID 17267614; PMID 19298661; PMID 35287700; PMID 36631218; PMID 28647906; PMID 37509548. Proteolytic activation: PMID 14671324. Structural work with follistatin: PMID 19644449. Analytical method development for GDF8 and GDF11 discrimination: PMID 32104967. Human observational: PMID 30165829. NO registered human interventional trial of exogenous GDF-8 or GDF-11 was identified; human trials in this pathway have been of INHIBITORS — ACE-031 and bimagrumab — and not of the ligands. No approval in any jurisdiction. Safety literature for this pathway exists and is tracked under regulatory monitoring rather than restated in a product record.

4 Storage & specification

Storage

Recombinant mature-domain proteins of this class are supplied lyophilized, commonly from an acidified or carrier-containing buffer because the mature dimers have poor solubility at neutral pH, and this article is held that way: desiccated and light-protected at -20 degrees C to -80 degrees C, with -80 degrees C used for long-held material. Solutions are unstable at ambient temperature and do not tolerate freeze-thaw cycling, so the lot record carries a documented freeze-thaw limit and an in-solution stability window alongside the temperature.

Shelf life

The retest interval is set from the stability-indicating attributes for this molecule class, which are aggregation and disulfide scrambling, both read under the panel P4 additions: size-exclusion for aggregate content, and paired non-reducing and reducing analysis for disulfide state. Research purity for this class is typically specified as not less than 95 percent by SDS-page, and the position adopted here is that size-exclusion aggregate content, not a purity percentage, is the meaningful specification for the class, so it is the aggregate figure and not the gel percentage that governs the date carried on a lot.