Classic small proteins for teaching

Small, well-behaved proteins are ideal for learning how to read a structure: they load instantly and every helix and strand is easy to follow. Many of these, such as crambin, ubiquitin, BPTI and lysozyme, have been used for decades to test methods in crystallography, NMR, protein folding and computer simulation. Start here if you are new to molecular structures.

Open Crambin in 3D

25 structures

Crambin1CRN
A tiny plant protein of 46 residues that forms exceptionally well-ordered crystals.
Crambin at 0.48 Å resolution3NIR
Ubiquitin1UBQ
The small tag that marks proteins for destruction by the proteasome.
Hen egg-white lysozyme1LYZ
Sperm whale myoglobin1MBN
Bovine pancreatic trypsin inhibitor (BPTI)5PTI
Trp-cage miniprotein1L2Y
Only 20 residues, a favorite test case for protein folding simulations.
Villin headpiece subdomain1VII
Engrailed homeodomain1ENH
Protein G B1 domain1PGA
SH3 domain1SHG
Chymotrypsin inhibitor 2 (CI2)2CI2
Rop protein, a four-helix bundle1ROP
GCN4 leucine zipper coiled coil2ZTA
Tenascin fibronectin type III domain1TEN
Rubredoxin4RXN
Horse heart cytochrome c1HRC
Tuna cytochrome c3CYT
E. coli thioredoxin2TRX
Calmodulin3CLN
Calmodulin wrapped around a target peptide2BBM
Streptavidin bound to biotin1STP
One of the strongest non-covalent interactions known.
Barnase bound to barstar1BRS
Collagen-like peptide triple helix1BKV
Top7, a computer-designed protein with a new fold1QYS

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