Extracellular secretion of STa heat‐stable enterotoxin by Escherichia coli after fusion to a heterologous leader peptide

FEBS Letters

Sanchez, J.²  Solorzano, R.M.²  Holmgren, J.¹ 

[1] Department of Medical Microbiology and Immunology, University of Gothenburg, Guldhedsgatan 10A, Gotbenburg, S-41346, Sweden;Centro de Investigación sobre Enfermedades Infecciosas, Instituto Nacional de Salud Pública, Av Universidad 655, Col. Sta. Maria Ahuacatitlan, Cuernavaca, Morelos, 62508 Mexico

关键词: Synthetic gene;    Conotoxin GI;    Precursor peptide;    Enterotoxin B-subunit (E. coli);    Cysteine-rich peptide;   

DOI  :  10.1016/0014-5793(93)80885-X

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The mature 19-amino acid STa heat-stable enterotoxin of E. coli has a preceding peptide of 53 amino acids which contains two domains called Pre (aa 1–19) and Pro (aa 20–53) sequences, proposed to be essential for extracellular toxin release by this host. The Pro sequence, however, has been proven not be indispensable for this process since Pro deletion mutants secrete STa. To find out if Pre and/or other unremoved natural STa flanking sequences are responsible for toxin secretion in those mutants we genetically fused mature STa directly to the leader peptide of the periplasmic E. coli heat-labile enterotoxin B-subunit (LTB). Expression of this gene fusion resulted in extracellular secretion of biologically active STa by E. coli independently of natural STa neighboring genetic sequences. Moreover, these results suggest that STa might be able to gain access to the extracellular milieu simply upon its entry into the E. coli periplasm once guided into this compartment by the LTB leader peptide. To test if extracellular secretion in this fashion might be extended to other disulfide bond-rich small peptides, the 13 amino acid conotoxin GI and a non-enterotoxic STa-related decapeptide were cloned. None of the two peptides was found in culture supernatants, in spite of high structural homology to the toxin. Failure to be secreted most likely leads to degradation as peptides were also not detected in bacterial sonicates. We hypothesize that cysteine-rich peptides must have an amino acid length and/or number of disulfide bridges closer to those in STa for them to follow this toxin secretory pathway in E. coli.

【 授权许可】

Unknown