title: Disabling the folding catalyst is the last critical step in alpha-lytic protease folding.
abstract: Alpha-Lytic protease (alphaLP) is an extracellular bacterial pro-protease marked by extraordinary conformational rigidity and a highly cooperative barrier to unfolding. Although these properties successfully limit its proteolytic destruction, thereby extending the functional lifetime of the protease, they come at the expense of foldability (t(1/2) = 1800 yr) and thermodynamic stability (native alphaLP is less stable than the unfolded species). Efficient folding has required the coevolution of a large N-terminal pro region (Pro) that rapidly catalyzes alphaLP folding (t(1/2) = 23 sec) and shifts the thermodynamic equilibrium in favor of folded protease through tight native-state binding. Release of active alphaLP from this stabilizing, but strongly inhibitory, complex requires the proteolytic destruction of Pro. alphaLP is capable of initiating Pro degradation via cleavage of a flexible loop within the Pro C-terminal domain. This single cleavage event abolishes Pro catalysis while maintaining strong native-state binding. Thus, the loop acts as an Achilles' heel by which the Pro foldase machinery can be safely dismantled, preventing Pro-catalyzed unfolding, without compromising alphaLP native-state stability. Once the loop is cleaved, Pro is rapidly degraded, releasing active alphaLP.
authors.affiliation: Howard Hughes Medical Institute and the Department of Biochemistry and Biophysics, University of California at San Francisco, 600 16th Street, Room S412, San Francisco, CA 94143-2240, USA.
authors.forename: Erin L
authors.initials: EL
authors.lastname: Cunningham
authors.forename: David A
authors.initials: DA
authors.lastname: Agard
mesh_terms: D001665:Binding Sites; D002384:Catalysis; D004795:Enzyme Stability; D007700:Kinetics; D017510:Protein Folding; D011498:Protein Precursors / Q000737:chemistry / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D012697:Serine Endopeptidases / Q000737:chemistry* / Q000378:metabolism*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013816:Thermodynamics; D044166:Xanthomonadaceae / Q000201:enzymology*
chemical_list: D011498:Protein Precursors; D012697:Serine Endopeptidases; C021826:myxobacter alpha-lytic proteinase