 |
 |
Dear all, i have a 30 kDa protein that crystallize so far in three different conditions but with the same space group. It initially looks like tetragonal (I4, a=141, b=141, c=208) and then results triclinic (P1, a=141, b=141 c=144, alpha=119, beta=119, gamma=90), hosting about 24 mol. in the unit cell. Other data: self rotation shows the presence of 4 peaks with chi=180; molecular replacement shows the presence of a pseudo-translation peak; DLS made at protein concentration close to crystal growth conditions shows a Rh compatible with something like a tetramer with low polydispersity (about 15%). Do you have any experience with similar ‘asymmetric’ associations? Do you have any suggestions, beside the addition of ligands to the crystal growth conditions, in order to get a ‘simpler’ crystallographic assembly? I have some models (with sequence identity less than 25%) in order to try MR but all trials so far did not solve the structure (using balbes, molrep, phaser and epmr). Any suggestion is welcome. Thank you, Mario Milani