title: Role of ionic interactions and linker in the domain interaction and modulation of functional activity of hyaluronate lyases.
abstract: Hyaluronate lyases from Streptococcus pneumoniae (SpnHL) and Streptococcus agalactiae (SagHL) are composed of four domains; N-terminal domain, spacer domain, alpha-domain and C-terminal domain, which are connected through peptide linkers. We have earlier shown that the recombinant alpha- and C-terminal domains of SpnHL/SagHL interact with each other even in absence of the linker and form a functional complex with enhanced enzymatic activity. Here, we looked into the role of ionic interactions in the enzyme stability and also the role of C-terminal domain and linker in the functional regulation. Domain swapping studies showed that the C-terminal domain does not bind directly to the substrate; instead the domain contributes to the interaction with the polymeric hyaluronan for catalysis. Furthermore, the substrate specificity exchanges with the size of catalytic cleft. The role of linker connecting alpha-domain to C-terminal domain was found to hold the C-terminal domain in a conformation suitable for achieving maximum activity.
authors.affiliation: Molecular and Structural Biology Division, Central Drug Research Institute, Lucknow 226 001, India.
authors.forename: Md Sohail
authors.initials: MS
authors.lastname: Akhtar
authors.forename: Vinod
authors.initials: V
authors.lastname: Bhakuni
mesh_terms: D001665:Binding Sites; D004789:Enzyme Activation; D004795:Enzyme Stability; D007477:Ions; D011133:Polysaccharide-Lyases / Q000737:chemistry* / Q000145:classification / Q000378:metabolism*; D011485:Protein Binding; D011489:Protein Denaturation; D017434:Protein Structure, Tertiary; D013292:Streptococcus agalactiae / Q000201:enzymology*; D013296:Streptococcus pneumoniae / Q000201:enzymology*; D013329:Structure-Activity Relationship
chemical_list: D007477:Ions; D011133:Polysaccharide-Lyases; C100002:hyaluronate lyase