Sterols and triterpenes are structurally diverse bioactive molecules generated through cyclization of linear 2,3-oxidosqualene. Based on carbocationic intermediates generated during initial substrate preorganization s...Sterols and triterpenes are structurally diverse bioactive molecules generated through cyclization of linear 2,3-oxidosqualene. Based on carbocationic intermediates generated during initial substrate preorganization step, oxidosqualene cyclases （OSCs） are roughly segregated into protosteryl cation group that mainly catalyzes tetracyclic products and dammarenyl cation group which mostly generates pentacyclic products. However, in contrast to well-studied cascade of ring-forming reactions, little is known about the mechanism underlying the initial sub- strate folding process. Previously, we have identified a cucurbitadienol synthase （Bi） and its null allele bi （C393Y） from cucumber. By integration of homology modeling, residue coevolution and site-directed mutagenesis, we discover that four covarying amino acids including C393 constitute a dynamic domain that may be involved in substrate folding process for Bi. We also reveal a group of co-conserved residues that closely associated with the segregation of plant OSCs. These residues may act col- laboratively in choice of specific substrate folding inter- mediate for OSCs. Thus, engineer plant OSCs from into five-ringed producer. our findings open a door to four-ringed skeleton catalysts展开更多
基金supported by funding from the National Natural Science Foundation of China (31401886)the Agricultural Science and Technology Innovation Program
文摘Sterols and triterpenes are structurally diverse bioactive molecules generated through cyclization of linear 2,3-oxidosqualene. Based on carbocationic intermediates generated during initial substrate preorganization step, oxidosqualene cyclases （OSCs） are roughly segregated into protosteryl cation group that mainly catalyzes tetracyclic products and dammarenyl cation group which mostly generates pentacyclic products. However, in contrast to well-studied cascade of ring-forming reactions, little is known about the mechanism underlying the initial sub- strate folding process. Previously, we have identified a cucurbitadienol synthase （Bi） and its null allele bi （C393Y） from cucumber. By integration of homology modeling, residue coevolution and site-directed mutagenesis, we discover that four covarying amino acids including C393 constitute a dynamic domain that may be involved in substrate folding process for Bi. We also reveal a group of co-conserved residues that closely associated with the segregation of plant OSCs. These residues may act col- laboratively in choice of specific substrate folding inter- mediate for OSCs. Thus, engineer plant OSCs from into five-ringed producer. our findings open a door to four-ringed skeleton catalysts
