title: Enzyme kinetics of the human norovirus protease control virus polyprotein processing order.
abstract: The human norovirus (NoV) polyprotein is cleaved into mature non-structural proteins by both mature NoV protease (Pro, NS6) and its un-cleaved precursor (ProPol, NS6-7). Processing order is well-established with 'early' and 'late' cleavages, but the governing enzymatic mechanisms are unknown. Enzyme kinetics of a GII Pro and ProPol were analyzed using synthetic peptides representing the five natural polyprotein cleavage sites. The relative efficiency of cleavage of the individual peptides was consistent with established polyprotein processing order, and primarily correlated with enzyme turnover (kcat). Enzymatic efficiencies (kcat/Km) of ProPol at all five sites were equivalent to, or greater than, that of Pro. Binding affinities (Km) for the two least efficiently cleaved sites (p20/VPg, VPg/Pro) were 2-4-fold higher than the other sites. This work further defines the role of ProPol in NoV polyprotein cleavage, and demonstrates that human norovirus polyprotein processing order is primarily an inherent property of enzymatic activity.
authors.affiliation: Department of Microbiology and Immunology, Georgetown University Medical Center, Washington DC 20057, USA.
authors.forename: Jared
authors.initials: J
authors.lastname: May
authors.forename: Brent
authors.initials: B
authors.lastname: Korba
authors.forename: Alexei
authors.initials: A
authors.lastname: Medvedev
authors.forename: Prasanth
authors.initials: P
authors.lastname: Viswanathan
mesh_terms: D006801:Humans; D007700:Kinetics; D029322:Norovirus / Q000502:physiology*; D010447:Peptide Hydrolases / Q000378:metabolism*; D020815:Polyproteins / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D014764:Viral Proteins / Q000378:metabolism*
chemical_list: D020815:Polyproteins; D014764:Viral Proteins; D010447:Peptide Hydrolases
keywords: Enzyme kinetics; Norovirus; Polyprotein; Processing order; Protease