Fig. 4: Alignment of the deduced amino acid sequences of LsoTPS-1, LsoTPS-2, and LsoTPS-3.

The N-terminal transit peptide and conserved amino acid motifs RRX8W, RX8W (missing in LsoTPS-3 due to the alternative splicing), DDXXD, and NSE/DTE are indicated. RRX8W has been suggested to facilitate the isomerization–cyclization reaction10. DDXXD and NSE/DTE are speculated to form the binding site for the substrate (GPP)–divalent metal cation (Mg2+, Mn2+, etc.)32. RX8W is speculated to be the substrate-binding pocket according to an NCBI CD search (https://www.ncbi.nlm.nih.gov/Structure/cdd/wrpsb.cgi?tdsourcetag)