Re: [ccp4bb] non-symmetric tetramer ?

[Roger Rowlett]

The symmetry of a homotetramer will depend (in part) on how many types of interfaces it has. Some sort of 2-fold symmetry is probably more likely. Crystallization unit cell is another matter, and depends on contact interfaces. We study a protein that is a homotetramer that has two different dimer interfaces (a "dimerization" and a "tetramerization" interface) giving a biological unit with multiple 2-fold axes. So far, it will crystallize in unit cells C2, a "double-size" C2 on c, C222(1), P4(1)2(1)2, P6(5), P3(2), and I2(1)2(1)2(1) depending on the variant and ligands bound. My students seem extra-talented in generating new unit cells and space groups of the same protein for us to puzzle out via MR. Cheers. On 7/28/2010 2:31 PM, Fred wrote: Dear CCP4bb, Could someone please, point me to some references about non-symmetric tetramers? If I have a tetramer composed by 4 identical subunits, it'll always have a P4 point group symmetry? Thank in advance, Tomb -- Roger S. Rowlett Professor Department of Chemistry Colgate University 13 Oak Drive Hamilton, NY 13346 tel: (315)-228-7245 ofc: (315)-228-7395 fax: (315)-228-7935 email: rrowl...@colgate.edu