Signal peptide mutants ofEscherichia coli

Abstract

Numerous secretory proteins of the Gram-negative bacteria E. coli are synthesized as precursor proteins which require an amino terminal extension known as the signal peptide for translocation across the cytoplasmic membrane. Following translocation, the signal peptide is proteolytically cleaved from the precursor to produce the mature exported protein. Signal peptides do not exhibit sequence homology, but invariably share common structural features: (1) The basic amino acid residues positioned at the amino terminus of the signal peptide are probably involved in precursor protein binding to the cytoplasmic membrane surface. (2) A stretch of 10 to 15 nonpolar amino acid residues form a hydrophobic core in the signal peptide which can insert into the lipid bilayer. (3) Small residues capable of beta-turn formation are located at the cleavage site in the carboxyl terminus of the signal peptide. (4) Charge characteristics of the amino terminal region of the mature protein can also influence precursor protein export. A variety of mutations in each of the structurally distinct regions of the signal peptide have been constructed via site-directed mutagenesis or isolated through genetic selection. These mutants have shed considerable light on the structure and function of the signal peptide and are reviewed here.

Protein secretion and the pathogenesis of bacterial infections

“…Proteins destined for transport by this pathway are synthesized as signal peptide bearing precursors (Lingappa and Blobel 1980;Silhavy et al 1983;Gennity et al 1990). Signal peptides are generally positioned at the N terminus and consist of one or more positively charged amino acids followed by a stretch of 10-20 hydrophobic amino acids (Silhavy et al 1983;Gennity et al 1990). Once the precursors have been translocated across the membrane, the signal peptides are removed by signal peptidase (Chang et al 1982;Dalbey and Wickner 1985).…”

Studies on the Formation of Murein-Bound Lipoprotein in Escherichia coli

“…Mutant prolipoproteins LppD14 (Lin et ~., 1978), R14 (Gennity et al, 1990), L20, V20 (Pollitt et al, 1986), G21…”

“…The peptidoglycan of mutant lRUD14 was shown to contain a greatly reduced amount of mature lipoprotein but 74 no prolipoprotein (Lin et ~., 1980b). substitution of Gly14 with a positively charged arginine was found to affect the modification and processing of prolipoprotein (Gennity et al, 1990). The formation of bound-form lipoprotein in mutant lR2R14 was studied in this thesis.…”

Export of a hyperexpressed mammalian globular cytochrome b5 precursor in Escherichia coli is dramatically affected by the nature of the amino acid flanking the secretory signal sequence cleavage bond

“…Single point mutations particularly those involving insertion of a charged residue(s) in the hydrophobic core prove to be most deleterious. 20,21 A more recent proteomic study of the human genome has also demonstrated that singlenucleotide polymorphism in SSs correlate with pathogenesis accruing from cessation of secretion of the proteins. 22 While SSs have a variable primary structure, the analysis of their role in secretion is compounded by the fact that each class of the secretory protein also has a different N-terminal mature protein sequence.…”