Malonyl-CoA: acyl carrier protein transacylase (MCAT) is a critical enzyme responsible for the transfer
of the malonyl moiety to holo-acyl carrier protein (ACP) forming the malonyl-ACP intermediates in the
initiation step of type II fatty acid synthesis (FAS II) in bacteria. MCAT has been considered as an
attractive drug target in the discovery of antibacterial agents. In this study, the crystal structure of MCAT
from Helicobacter pylori (Hp) at 2.5 A resolution is reported, and the interaction of HpMCAT with
HpACP is extensively investigated by using computational docking, GST-pull-down, and surface plasmon
resonance (SPR) technology-based assays. The crystal structure results reveal that HpMCAT has a compact
folding composed of a large subdomain with a similar core as in a/b hydrolases, and a similar ferredoxin-like
small subdomain as in acylphosphatases. The docking result suggests two positively charged areas near the
entrance of the active site of HpMCAT as the ACP-binding region. Binding assay research shows that
HpMCAT demonstrates a moderately binding ability against HpACP. The solved 3D structure of HpMCAT is
expected to supply useful information for the structure-based discovery of novel inhibitors against MCAT, and
the quantitative study of HpMCAT interaction with HpACP is hoped to give helpful hints in the understanding
of the detailed catalytic mechanisms for HpMCAT.