Attacin--an insect immune protein--binds LPS and triggers the specific inhibition of bacterial outer-membrane protein synthesis.
Attacin is a 20 kDa antibacterial protein, originally isolated from the immune haemolymph of Hyalophora cecropia. It has been demonstrated previously that attacin causes increased permeability of the outer membrane of Escherichia coli and inhibition of outer-membrane protein synthesis at the transcriptional level. This is accompanied by inhibition of growth. Here, LPS is shown to serve as the receptor for attacin and evidence is presented that attacin does not need to enter the cell to exert its activity. The increase in outer-membrane permeability precedes any increase in inner-membrane permeability by at least one generation time (approximately 45 min), and the inhibiting effect of attacin on synthesis of outer-membrane proteins is detectable after only 10 min. It is also shown that attacin causes induction of several stress proteins and increased synthesis of LPS within, respectively, 25 and 60 min of treatment. Based on the results presented, it is proposed that attacin has the unique ability to specifically interfere with synthesis of outer-membrane proteins without entering the inner membrane or cytoplasm.
Department of Medical Biochemistry & Microbiology, Uppsala UniversityBox 582, S-75123 UppsalaSweden.
Anette
A
Carlsson
Department of Microbiology, Lund UniversitySölveg. 12, S-22362 LundSweden.
Thomas
T
Nyström
Department of Molecular Cell Biology, Institute of Biomembranes, Utrecht UniversityPadualaan 8, 3584 CH UtrechtThe Netherlands.
Hans
H
de Cock
Department of Medical Biochemistry & Microbiology, Uppsala UniversityBox 582, S-75123 UppsalaSweden.
Hans
H
Bennich
D000818:Animals; D001425:Bacterial Outer Membrane Proteins / Q000037:antagonists & inhibitors* / Q000096:biosynthesis*; D004926:Escherichia coli / Q000276:immunology*; D006360:Heat-Shock Proteins; D006458:Hemolymph / Q000276:immunology; D019476:Insect Proteins / Q000378:metabolism* / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000096:biosynthesis / Q000378:metabolism* / Q000494:pharmacology; D008274:Magnesium / Q000494:pharmacology; D033903:Periplasmic Proteins; D011113:Polymyxins / Q000378:metabolism; D011485:Protein Binding; D012697:Serine Endopeptidases / Q000378:metabolism
D001425:Bacterial Outer Membrane Proteins; D006360:Heat-Shock Proteins; D019476:Insect Proteins; D008070:Lipopolysaccharides; D033903:Periplasmic Proteins; D011113:Polymyxins; C039711:attacin antibacterial protein, insect; C061682:DegP protease; D012697:Serine Endopeptidases; D008274:Magnesium