title: Role of N-terminal amino acids in the potency of anthrax lethal factor.
abstract: Anthrax lethal factor (LF) is a Zn(+2)-dependent metalloprotease that cleaves several MAPK kinases and is responsible for the lethality of anthrax lethal toxin (LT). We observed that a recombinant LF (LF-HMA) which differs from wild type LF (LF-A) by the addition of two residues (His-Met) to the native Ala (A) terminus as a result of cloning manipulations has 3-fold lower potency toward cultured cells and experimental animals. We hypothesized that the "N-end rule", which relates the half-life of proteins in cells to the identity of their N-terminal residue, might be operative in the case of LF, so that the N-terminal residue of LF would determine the cytosolic stability and thereby the potency of LF. Mutational studies that replaced the native N-terminal residue of LF with known N-end rule stabilizing or destabilizing residues confirmed that the N-terminal residue plays a significant role in determining the potency of LT for cultured cells and experimental animals. The fact that a commercially-available LF preparation (LF-HMA) that is widely used in basic research studies and for evaluation of vaccines and therapeutics is 3-fold less potent than native LF (LF-A) should be considered when comparing published studies and in the design of future experiments.
authors.affiliation: Laboratory of Bacterial Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America.
authors.forename: Pradeep K
authors.initials: PK
authors.lastname: Gupta
authors.forename: Mahtab
authors.initials: M
authors.lastname: Moayeri
authors.forename: Devorah
authors.initials: D
authors.lastname: Crown
authors.forename: Rasem J
authors.initials: RJ
authors.lastname: Fattah
authors.forename: Stephen H
authors.initials: SH
authors.lastname: Leppla