SH3 (SRC Homology 3) domains are a type of protein structure found widely in nature:
http://en.wikipedia.org/wiki/SH3_domain

This SH3 domain is from c-Src specific tyrosine kinase. Model based on the Protein Data Bank entry 1CSK:
http://www.rcsb.org/pdb/explore.do?structureId=1CSK

Model created using VMD:
http://www.ks.uiuc.edu/Research/vmd/

Successfully printed in PLA on a Makerbot Replicator2 using MakerWare 2.2.2.89, standard resolution with 3 shells and 25% infill. Use rafts and supports.