Isolation and functional analysis of histidine-tagged elongation factor Tu.

The study of the structure/function relationships of the Escherichia coli elongation factor Tu (EF-Tu) via mutagenesis has been hampered by difficulties encountered in separating the mutated factor from other proteins, in particular native EF-Tu. Here we describe a novel system for the purification of EF-Tu mutant species, based on metal-ion affinity chromatography. To facilitate rapid and efficient purification we designed a recombinant EF-Tu with an additional C-terminal sequence of one serine and six histidine residues. A cell extract containing the His-tagged EF-Tu (EF-TuHis) is applied to a Ni(2+)-nitrilotriacetic acid column. EF-TuHis can be selectively eluted with an imidazole containing buffer, yielding a preparation of more than 95% purity, free of wild-type EF-Tu. In-vitro and in-vivo functional analyses show that EF-TuHis resembles the wild-type EF-Tu, which makes this one-step isolation procedure a promising tool for the study of the interactions of mutant EF-Tu with the various components of the elongation cycle. The new isolation procedure was successfully applied for the purification of a mutant EF-TuHis with a Glu substitution for Lys237, a residue possibly involved in the binding of aminoacyl-tRNA.

Parturition and pelvic fracture. Follow-up of 34 obstetric patients with a history of pelvic fracture.

Thirty-four women with a history of pelvic fracture gave birth. Ten had experienced increasing or recurrent pain during the course of their pregnancy. Twenty-seven women gave birth without complications, including 13 patients with displaced pelvis. In only one patient was cesarean section carried out on suspicion of disproportion. Cesarean section was carried out in another case because of resymphysiolysis and in one because of other complications to the pregnancy. Two underwent vacuum extraction because of secondary inertia, but subsequently they gave birth by the vaginal route without complications. In connection with pregnancy and birth, 2 patients had resymphysiolysis. They were the only patients of 8 with symphysiolysis who had undergone osteosynthesis, and both had had the material removed before pregnancy. It is concluded that separation of the symphysis in a pelvic fracture is a more serious complication in subsequent parturition than is displacement of the bony birth canal.