Nucleotide sequence of bglC, the gene specifying enzymeIIbgl of the PEP:sugar phosphotransferase system in Escherichia coli K12, and overexpression of the gene product

The EnzymeIIbgl of the phosphoenolpyruvate- (PEP-) dependent phosphotransferase system catalyses the uptake and concomitant phosphorylation of beta-glucosides by Escherichia coli; it is specified by the gene bglC. The nucleotide sequence of a 3.6 kb HindIII restriction fragment spanning bglC, cloned on a plasmid, was determined. DNA analysis strongly suggests that the published order of this and other genes involved in beta-glucoside utilization, bgl C, S, B, is incorrect, and that the regulatory gene bglS may be located upstream of the structural genes bglC and bglB. From the deduced amino acid sequence it is predicted that the membrane protein specified by bglC consists of 625 amino acid residues (66.48 kDa). The protein has the hydropathic profile expected of an integral membrane protein (average hydropathy = 0.62). Comparisons between the amino acid sequences deduced for the EnzymeIIbgl and for the mannitol-specific EnzymeIImtl show that these proteins are related, and a little direct homology is apparent. A 2.3 kb AluI fragment spanning bglC was subcloned into an expression vector which carries the lambda PL promoter and then transformed into a host strain which produces thermolabile cI857 repressor and the anti-terminator N; thermoinduction resulted in the overproduction of a membrane protein and the appearance of Bgl activity.     

Elimination of nurse cell nuclei that shuttle into oocytes during oogenesis

Drosophila oocytes develop together with 15 sister germline nurse cells (NCs), which pass products to the oocyte through intercellular bridges. The NCs are completely eliminated during stages 12–14, but we discovered that at stage 10B, two specific NCs fuse with the oocyte and extrude their nuclei through a channel that opens in the anterior face of the oocyte. These nuclei extinguish in the ooplasm, leaving 2 enucleated and 13 nucleated NCs. At stage 11, the cell boundaries of the oocyte are mostly restored. Oocytes in egg chambers that fail to eliminate NC nuclei at stage 10B develop with abnormal morphology. These findings show that stage 10B NCs are distinguished by position and identity, and that NC elimination proceeds in two stages: first at stage 10B and later at stages 12–14.