PMID: 20196071

Authors:

Kefala G, Ahn C, Krupa M, Esquivies L, Maslennikov I, Kwiatkowski W, Choe S

Title:

Structures of the OmpF porin crystallized in the presence of foscholine-12.

Journal:

Protein Sci. 2010 Mar 1.

Abstract:

The endogenous Escherichia coli porin OmpF was crystallized as an accidental by-product of our efforts to express, purify and crystallize the Escherichia coli integral membrane protein KdpD in the presence of foscholine-12. Foscholine-12 is widely used in membrane protein studies, but no crystal structure of a protein that was both purified and crystallized with this detergent has been reported in PDB. Crystallization screening for KdpD yielded two different crystals of contaminating protein OmpF. Here we report two OmpF structures, the first membrane protein crystal structures for which extraction, purification and crystallization were done exclusively with foscholine-12. The first structure was refined in space group P21 with cell parameters a = 136.7 A, b = 210.5 A, c = 137 A and beta = 100.5 degrees , and the resolution of 3.8 A. The second structure was solved at the resolution of 4.4 A and was refined in the P321 space group, with unit-cell parameters a = 215.5 A, b = 215.5 A, c = 137.5 A and gamma = 120 degrees . Both crystal forms show novel crystal packing, in which the building block is a tetrahedral arrangement of four trimers. Additionally we discuss the use of foscholine-12 for membrane protein crystallization and structure determination, as well as the problem of the OmpF contamination for membrane proteins overexpressed in E. coli.