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[Biochemistry](https://durgical.com/en/biochemistry/) · Protein

# Fibrillin-1

Fibrillin-1 forms microfibrils that support elastic fibres and store TGF-β; its variants cause Marfan syndrome.

Updated 2026-11-01

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## Key facts

- Large glycoprotein (≈ 2,870 amino acids, FBN1 gene on chromosome 15) made mostly of calcium-binding EGF-like domains (cbEGF).
- Forms ≈ 10 nm microfibrils: the scaffold for elastin and the main component of the zonular fibres that hold the lens.
- Holds TGF-β in a latent form in the matrix; when fibrillin fails, TGF-β signalling rises in the aortic wall.
- Dominant FBN1 variants cause Marfan syndrome: aortic root dilation, upward lens dislocation and tall stature with long limbs.

**Also called**
FBN1, Microfibrils

**Genes**
FBN1

**Structure (PDB)**
[1UZJ](https://www.rcsb.org/structure/1UZJ)

## Structure

- Structure 1UZJ is a human fibrillin-1 fragment (cbEGF22–TB4–cbEGF23) with calcium ions; calcium stiffens the cbEGF domains.
- The TB4 domain of this fragment carries the RGD sequence that binds cell integrins.

## Regulation

- Secreted by fibroblasts, smooth-muscle cells and lens cells; assembled into microfibrils outside the cell.
- Many Marfan variants change a cysteine or a calcium-binding residue, so the domain misfolds or is degraded early.

## Inhibitors and toxins

- Loss of calcium from cbEGF domains (more protease-sensitive)
- Dominant-negative FBN1 variants

## Clinical notes

- Marfan syndrome: risk of aortic dissection; the aortic root is followed by echocardiography and blood pressure is controlled.
- Lens dislocation in Marfan is typically upward (in homocystinuria, downward).
- FBN1 variants also cause short-stature dysplasias with thick skin (acromicric and geleophysic dysplasia).

## Related conditions

- [Aortic dissection](https://durgical.com/en/conditions/aortic-dissection/)
- [Ehlers–Danlos syndrome](https://durgical.com/en/conditions/ehlers-danlos-syndrome/)

## Related

- [Elastin](https://durgical.com/en/biochemistry/enzymes/elastin/)
- [Collagen](https://durgical.com/en/biochemistry/enzymes/collagen/)
- [Collagen synthesis](https://durgical.com/en/biochemistry/topics/collagen-synthesis/)
- [Protein structure and folding](https://durgical.com/en/biochemistry/topics/protein-structure-and-folding/)

## Test yourself

Think of the answer, then tap the question to see it.

## Which gene is altered in Marfan syndrome?

FBN1, which encodes fibrillin-1; inheritance is autosomal dominant.

## Why does loss of fibrillin-1 harm the aorta beyond weakening it?

Fibrillin holds latent TGF-β; without it TGF-β signalling rises, which degrades the wall and dilates the aortic root.

## Which way does the lens dislocate in Marfan syndrome?

Upward and outward, because the fibrillin zonular fibres break; in homocystinuria it usually goes downward.

## Which ion stabilises fibrillin's cbEGF domains?

Calcium; without it the domains become floppy and are degraded more easily.

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Educational information, not medical advice. For any symptom, see a health professional.

Sources: [FBN1: Fibrillin-1 (human)](https://www.uniprot.org/uniprotkb/P35555/entry) (UniProt, 2026); [FBN1 gene: MedlinePlus Genetics](https://medlineplus.gov/genetics/gene/fbn1/) (MedlinePlus, US National Library of Medicine, 2026); [Marfan syndrome: MedlinePlus Genetics](https://medlineplus.gov/genetics/condition/marfan-syndrome/) (MedlinePlus, US National Library of Medicine, 2026); [1UZJ: Integrin binding cbEGF22-TB4-cbEGF33 fragment of human fibrillin-1, holo form.](https://www.rcsb.org/structure/1UZJ) (RCSB Protein Data Bank, 2026); [Elastic fibre formation](https://reactome.org/PathwayBrowser/#/R-HSA-1566948) (Reactome, 2026); Textbook of Biochemistry for Medical Students, 6th ed. (Jaypee Brothers Medical Publishers (Vasudevan DM, Sreekumari S, Vaidyanathan K), 2011).

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Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/biochemistry/enzymes/fibrillin-1/