Ramanuj, This is definitely possible. Cases of "intertwined homodimers" are rare, but there are several known structures that demonstrate this phenomenon, and they are very interesting (especially with respect to studying knotted proteins - see reference below). Examples are pdb IDs: 2ouf, 1myk, 2rh3.
A cool paper regarding intertwined homodimers and knotted proteins: Proc Natl Acad Sci U S A. 2010 Nov 30;107(48):20732-7. Epub 2010 Nov 10. Structure and folding of a designed knotted protein. King NP, Jacobitz AW, Sawaya MR, Goldschmidt L, Yeates TO. Your structure is very interesting. Mike ----- Original Message ----- From: "Ramanuj Banerjee" <ramanuj.baner...@saha.ac.in> To: CCP4BB@JISCMAIL.AC.UK Sent: Tuesday, April 26, 2011 12:37:29 AM GMT -08:00 US/Canada Pacific Subject: [ccp4bb] problem with pdb & its symmetry molecule Dear All, I have solved a protein structure (experimentally phased) with 1 molecule in the asymmetric unit at 2.22 A (high resolution). The present R factor is .22 and R free .27 with Ramachandran favoured >98% and R and R free are decreasing with refinement.The problem is: when the pdb is opened in pymol and symmetry mates generated, the upper part of the molecule shows to be intertwined with the symmetry molecule (attached .jpg), but there are no clashes in between the two.The electron density is so very fine that no alternative choices of chain flow are available.All the processes starting from phasing and refinement have been done in Phenix.Is such a thing possible ? [image/jpeg:a copy.jpg] -- Michael C. Thompson Graduate Student Biochemistry & Molecular Biology Division Department of Chemistry & Biochemistry University of California, Los Angeles mi...@chem.ucla.edu
