Enzymatic and molecular characteristics of the efficiency and specificity of exfoliative toxin cleavage of desmoglein 1.
Exfoliative toxins (ETs) from Staphylococcus aureus blister the superficial epidermis by hydrolyzing a single peptide bond, Glu381-Gly382, located between extracellular domains 3 and 4 of desmoglein 1 (Dsg1). Enzyme activity is dependent on the calcium-stabilized structure of Dsg1. Here we further define the characteristics of this cleavage. Kinetic studies monitoring the cleavage of Dsg1 by ETA, ETB, and ETD demonstrated kcat/Km values of 2-6 x 10(4) m(-1) s(-1), suggesting very efficient proteolysis. Proteolysis by ETA was not efficiently inhibited by broad spectrum serine protease inhibitors, suggesting that the enzyme cleavage site may be inactive or inaccessible before specific binding to its substrate. Using truncated mutants of human Dsg1 and chimeric molecules between human Dsg1 and either human Dsg3 or canine Dsg1, we show that for cleavage, human-specific amino acids from Dsg1 are necessary in extracellular domain 3 upstream of the scissile bond. If these residues are canine rather than human, ETA binds, but does not cleave, canine Dsg1. These data suggest that the exquisite specificity and efficiency of ETA may depend on the enzyme's binding upstream of the cleavage site with a very specific fit, like a key in a lock.
Hanakawa
Yasushi
Y
Department of Dermatology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA.
Schechter
Norman M
NM
Lin
Chenyan
C
Nishifuji
Koji
K
Amagai
Masayuki
M
Stanley
John R
JR
D000409:Alanine / Q000737:chemistry; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D015153:Blotting, Western; D015820:Cadherins / Q000737:chemistry / Q000502:physiology*; D018076:DNA, Complementary / Q000378:metabolism; D051183:Desmoglein 1; D004285:Dogs; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018698:Glutamic Acid / Q000737:chemistry; D005998:Glycine / Q000737:chemistry; D006801:Humans; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D010455:Peptides / Q000737:chemistry; D017354:Point Mutation; D016133:Polymerase Chain Reaction; D011233:Precipitin Tests; D011485:Protein Binding; D021382:Protein Sorting Signals; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry; D017386:Sequence Homology, Amino Acid; D012694:Serine / Q000737:chemistry; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology; D013211:Staphylococcus aureus / Q000378:metabolism; D013997:Time Factors; D014118:Toxins, Biological / Q000737:chemistry; D000511:alpha-Macroglobulins / Q000737:chemistry
D015820:Cadherins; D018076:DNA, Complementary; D051183:Desmoglein 1; D004791:Enzyme Inhibitors; D010455:Peptides; D021382:Protein Sorting Signals; D011994:Recombinant Proteins; D015842:Serine Proteinase Inhibitors; D014118:Toxins, Biological; D000511:alpha-Macroglobulins; D018698:Glutamic Acid; D012694:Serine; D000409:Alanine; D005998:Glycine