Structural insights into the calcium dependence of Stig cyclases.

ABSTRACT: The Stig cyclases from Stigonematalean cyanobacteria are classified as a novel type of calcium-dependent cyclases which catalyze an uncommon reaction cascade comprising Cope rearrangement, 6-exo-trig cyclization, and electrophilic aromatic substitution. Previously we found two calcium ions near the substrate-binding pocket. The calcium-coordinating residues are conserved in all Stig cyclases. In the present study, we use site-directed mutagenesis to investigate the role of calcium coordination. By individually mutating the coordinating residues in either of the Ca²⁺-binding sites to alanine, the enzyme activity is significantly reduced, suggesting that the presence of Ca²⁺ in both sites is essential for catalysis. Furthermore, the crystal structure of N1

SUBMITTER: Tang X 

PROVIDER: S-EPMC9063808 | biostudies-literature | 2019 Apr

REPOSITORIES: biostudies-literature