SUMO - the small ubiquitin-like modifier

Small ubiquitin-like modifier (SUMO), based on the first model from Bayer et al. (1998).

http://www.rcsb.org/pdb/explore/explore.do?structureId=1A5R

I opened the PDB file with UCSF's Chimera program, selected the first model chain then adjusted the ribbon characteristics to thicken the model, after which I exported it as an STL file (export scene). The model was rotated in (the more familiar) Blender.

Thanks to Aarono for his great molecular models and for the information on how to