Recent experimental results suggest that replicated daughter chromosomes (nucleoids) in Escherichia coli move non-progressively and abruptly at an early stage of the D (division) period from midcell toward the cell quarter positions, which will become the centres of the daughter cells. The chromosome positioning at the quarter positions was found to be controlled by the muk gene products. In muk mutants, normal size anucleate cells are spontaneously produced during cell division. The mukA gene is identical to the tolC gene encoding an outer membrane protein. The mukB gene codes for a 177-kDa protein. The amino acid sequence of the MukB protein deduced for the nucleotide sequence suggests that the MukB protein has five characteristic secondary structure domains: an amino-terminal globular domain containing a consensus sequence binding with ATP or another nucleotide. The central region of the protein consists of two alpha-helical coiled-coil domains and one globular domain. A carboxyl-terminal globular domain is rich in cysteine and positively charged residues arginine and lysine. Two MukB protein molecules might form a homodimer in the coiled-coil regions. The predicted secondary structure of the MukB protein suggests that the protein provides the force required for the positioning of nucleoids from midcell toward the cell quarters. The mukC and mukD genes are located at 88 and 41 min of the chromosome map, respectively.

Amino Acid Sequence↗

PubMedDate not supplied

Structure and function of the ftsH gene in Escherichia coli.

The ftsH mutant Y16 shows thermosensitive filamentation with reduced amounts of penicillin-binding protein 3 (PBP3) (Ferreira et al., 1987). Genetic analysis, however, showed that the lethality of the ftsH mutation was not due to a lack of PBP3 activity alone. The ftsH gene was cloned and sequenced and the FtsH protein was deduced to be a membrane protein of 70.7 kDa which has an ATP-binding domain. Highly significant homology of amino acid sequence was observed between FtsH protein and two eukaryotic proteins, yeast Saccharomyces cerevisiae Sec 18p and its mammalian homologue NSF, which are involved in protein transport pathways. This suggests that FtsH protein may act for translocation of specific proteins including PBP3 and at least one other additional protein essential for cell growth. Suppressor mutants of Y16, which were able to grow at 42 degrees C, were isolated, and the suppressor mutations (sfh) were mapped to 16 min. A wild type chromosomal fragment able to complement the sfh mutations was cloned. We also identified another gene (ftsJ) affecting cell division in the region upstream of the ftsH gene.

Bacterial Proteins↗

PubMedDate not supplied

Management of clubfoot deformity in amyoplasia.

Forty-one clubfeet in 22 patients with amyoplasia were studied retrospectively at a mean duration after surgery of 118 months (range, 45-253). The clubfeet were managed by a regimen including initial stretching casts, posteromedial release, and postoperative splinting at night. The mean age at the time of surgery was 7.3 months. Correction of deformity without recurrence was achieved in 11 (27%). Recurrent deformity was corrected by serial casting in eight feet and required secondary operative procedures in 20 feet. In the feet without recurrence of deformity, the duration of splinting at night after surgery was significantly longer than in those with recurrence (p < 0.05). At follow-up, 39 (95%) feet were plantigrade and were considered satisfactory. Our findings suggest that most clubfeet in amyoplasia can be effectively corrected by posteromedial release and that the recurrence of deformity can be reduced by splinting at night and often corrected by serial cast treatment.

Abnormalities, Multiple↗