Three chains wound into a rope, Gly-X-Y over and over, a
third of the protein in you. Six depositions, one camera.
the helix
For the scurvy lesson. 3B0S is the hydroxylated
control; 1K6F above it is the unhydroxylated one, and 1K6F is also what
the enzyme actually sees — prolyl 4-hydroxylase works on a single
unfolded chain, before any of this is wound.
one wrong residue
what holds on to it
4AU3 — collagen being made. Every other
entry is finished material or a fragment of it; this is the only one
inside a cell. Hsp47 binds the completed triple helix in the ER and lets
go in the Golgi as the pH drops.
the whole thing
what you are looking at
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assembly
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span
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modelled
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completeness
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hydroxylated
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helix / strand
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ss records
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bound
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drawn close up
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extents Å
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view
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The helix nobody records. Collagen's helix isn't
a PDB helix or sheet — it's polyproline II, three strands
coiled together — so half these files bake as pure coil,
told apart by colour instead.
Records that describe the wrong thing. Two of
the three files with SS records are annotating their
partner (the integrin domain, Hsp47), not collagen. Only
1CAG annotates a collagen chain at all.
Hydroxyproline hides as HETATM. It's every
third residue, so an ATOM-only trace (1CAG) drops most of it and
looks disordered rather than unread.
A third of the protein in you, and the reason skin, bone,
tendon and cornea hold their shape. Three chains, each a left-handed
polyproline helix, wound into a right-handed rope.
Gly-X-Y, forever. Glycine is the only residue
small enough for the crowded axis; Y is usually hydroxyproline,
made by an enzyme that needs vitamin C. Without it the helix is
unstable at body temperature — scurvy, not a missing
protein.
One substitution breaks it. Swap a glycine for
alanine and the helix can't close there. It's dominant: the bad
chain joins helices built from good chains and ruins them —
osteogenesis imperfecta.
Then it assembles. Molecules stagger by 67 nm
into fibrils, fibrils into fibres — the step no deposition
holds, and what makes tendon.
Turn the molecule, then copy.
Paste it into view.basis in proteins.js with
by: 'human'.