Putative catalytic domain, repeat 2, of Streptococcus mutans uncharacterized protein SMU_988 and similar proteins
Putative catalytic domain, repeat 2, of Streptococcus mutans uncharacterized protein SMU_988 and similar proteins. Although SMU_988 and similar proteins have not been functionally characterized, members in this subfamily show high sequence homology to bacterial cardiolipin (CL) synthases, which catalyze the reversible phosphatidyl group transfer between two phosphatidylglycerol molecules to form CL and glycerol. Members of this subfamily contain two HKD motifs (H-x-K-x(4)-D, where x represents any amino acid residue) that characterizes the phospholipase D (PLD) superfamily. The two motifs may be part of the active site and may be involved in phosphatidyl group transfer.
Comment:Based on similarity with phospholipase D, which functions as a bi-lobed monomer with two catalytic domains. Each domain carries one copy of the conserved HKD motif and two domains form a single active site.
Comment:The HKD signature motif (expanded to H-x-K-x(4)-D-x(6)-G-S/T-x-N in this subfamily, where x represents any amino acid residue) characterizes the PLD superfamily.
Comment:Most residues in the HKD motif are part of the active site.
Jiyao W et al.(2023). "The conserved domain database in 2023.",