[Changes in the composition of anionic membrane phospholipids influence the protein secretion and biogenesis of cell envelope in Escherichia coli].

The secretion of alkaline phosphatase (PhoA) and peculiarities of biogenesis of the cell envelope were studied in Escherichia coli strains HD30/pHD 102 and HDL11 with controlled synthesis of anionic phospholipids, phosphatidylglycerol, and cardiolipin. Inactivation of the pgsA gene encoding the synthesis of anionic phospholipids or changes in the regulation of its expression by an environmental factor caused changes in the metabolism and composition of membrane phospholipids, which resulted in a decrease in the secretion of alkaline phosphatase through the cytoplasmic membrane and an increase in PhoA secretion from the periplasm into the culture medium. A conforming increase was observed in exopolysaccharide secretion, as well as a decrease in the contents of lipopolysaccharide and lipopolyprotein of the outer membrane that determine the membrane barrier properties.

[The unbalance of membrane phospholipid composition of Escherichia coli affects the PPHO promoter activity].

Activity of phosphate PPHO or arabinose PBAD promoter of Escherichia coli has been studied depending on the content of zwitter-ionic phosphatidylethanolamine (PE) and anionic phospholipids in membranes. In the absence of PE or under significant decrease in the content of anionic phospholipids, there is a significant decline of PPHO promoter activity but not PBAD promoter. Since the PPHO promoter belongs to the Pho-regulon--a member of the family of two-component regulatory systems of signal transduction having membrane sensors, the regulation of gene expression by phospholipids is presumed to be realized through a membrane sensor.

[Interaction of effect on secretion of alkaline phosphatase from E. coli by charge of the N-terminal part of the signal peptide and proteins SecB and SecA].

The cytoplasmic step of posttranslational secretion in Escherichia coli is catalyzed by export-specific chaperone SecB and translocational ATPase SecA. In addition, the efficiency of secretion depends on the charge of the signal peptide (SP). Substitution of positively charged Lys(-20) with noncharged Ala or negatively charged Glu in the N-terminal region of SP of the alkaline phosphatase (PhoA) precursor (prePhoA) was shown to decrease the PhoA secretion in the periplasm.

[Inactivation of pgsA gene affects biosynthesis and secretion of Escherichia coli alkaline phosphatase].

Inactivation of pgsA, which is responsible for biosynthesis of anionic phospholipid phosphatidylglycerol (PG), was shown to affect biosynthesis and secretion of alkaline phosphatase (PhoA) in Escherichia coli. A decrease in PG, but not in total anionic phospholipids, correlated with reduction of PhoA secretion, suggesting the role of PG in this process. A dramatic decrease in PG (from 18 to 3, but not 8, percent of the total phospholipids) inhibited not only secretion, but also synthesis of PhoA.

[Interaction of SecB and SecA with the N-terminal region of mature alkaline phosphatase on its secretion in Escherichia coli].

Export-specific chaperone SecB and translocational ATPase SecA catalyze the cytoplasmic steps of Sec-dependent secretion in Escherichia coli. Their effects on secretion of periplasmic alkaline phosphatase (PhoA) were shown to depend on the N-terminal region of the mature PhoA sequence contained in the PhoA precursor. Amino acid substitutions in the vicinity of the signal peptide (positions +2, +3) not only dramatically inhibited secretion, but also reduced its dependence on SecB and SecA.