Pseudomonas exotoxin: recombinant conjugates as therapeutic agents.

Content Provider	Semantic Scholar
Author	Fitzgerald, David J. P. Pastan, Ira
Copyright Year	1992
Abstract	Pseudomonas exotoxin: structure and function Pseudornonas exotoxin (PE) is a bacterial protein produced by €3. aeruginosa that is toxic for most mammalian cells [for reviews see 1, 21. The mature protein is a proenzyme and, after activation, exhibits both NAD hydrolase activity and ADP-ribosyltransferase activity. When added to mammalian cells the toxin binds to the alpha 2-macroglobulin receptor which mediates internalization to the endosoma1 compartment [ 31. In the endosome the toxin is cleaved (‘nicked’) by a cellular protease. Disulphide bond reduction then results in the release of an enzymatically active toxin fragment which translocates to the cytosol where it inhibits protein synthesis. In the cytosol; PE hydrolyses NAD and transfers the ADP-ribose moiety of NAD to elongation factor 2 (EF-2). When EF-2 is modified in this way it can no longer participate in the synthesis of new protein. The inactivation of EF-2 is lethal for the cell. Structural analysis of PE crystals by McKay and colleagues [4] revealed three prominent domains. These were termed domains I, 11, and 111: domain I was further divided into domains Ia and Ib. This study was followed first by a deletion analysis of the structural gene [5] and then by many individual studies focused on determining the location of important sequences within each domain. The results from all these studies has revealed that domain Ia (amino acids 1-252) is responsible for the toxin binding to its surface receptor; domain I1 (amino acids 253-364) is the substrate for the cellular protease and, after cleavage, has translocating activity; domain Ib (amino acids 365-399) has no known function and most of it can be deleted without loss of toxin activity; and domain I11 (amino acids 400-61 3) has the ADP-ribosylating activity and contains an endoplasmic retention sequence. A closer look at the interactions of PE with cells has revealed that a lysine at position 57 in domain I is needed for cell binding [6]. Changing this basic residue to an acidic residue such as glutamic acid or inserting a dipeptide reduces binding by 100-fold. After binding the toxin is
File Format	PDF HTM / HTML
DOI	10.1042/bst0200731
PubMed reference number	1487051
Journal	Medline
Volume Number	20
Issue Number	4
Alternate Webpage(s)	http://www.biochemsoctrans.org/content/ppbiost/20/4/731.full.pdf
Alternate Webpage(s)	https://doi.org/10.1042/bst0200731
Journal	Biochemical Society transactions
Language	English
Access Restriction	Open
Content Type	Text
Resource Type	Article