Structure of the Plasmodium falciparum M17 aminopeptidase and significance for the design of drugs targeting the neutral exopeptidases.
Current therapeutics and prophylactics for malaria are under severe challenge as a result of the rapid emergence of drug-resistant parasites. The human malaria parasite Plasmodium falciparum expresses two neutral aminopeptidases, PfA-M1 and PfA-M17, which function in regulating the intracellular pool of amino acids required for growth and development inside the red blood cell. These enzymes are essential for parasite viability and are validated therapeutic targets. We previously reported the X-ray crystal structure of the monomeric PfA-M1 and proposed a mechanism for substrate entry and free amino acid release from the active site. Here, we present the X-ray crystal structure of the hexameric leucine aminopeptidase, PfA-M17, alone and in complex with two inhibitors with antimalarial activity. The six active sites of the PfA-M17 hexamer are arranged in a disc-like fashion so that they are orientated inwards to form a central catalytic cavity; flexible loops that sit at each of the six entrances to the catalytic cavern function to regulate substrate access. In stark contrast to PfA-M1, PfA-M17 has a narrow and hydrophobic primary specificity pocket which accounts for its highly restricted substrate specificity. We also explicate the essential roles for the metal-binding centers in these enzymes (two in PfA-M17 and one in PfA-M1) in both substrate and drug binding. Our detailed understanding of the PfA-M1 and PfA-M17 active sites now permits a rational approach in the development of a unique class of two-target and/or combination antimalarial therapy.
McGowan
Sheena
S
Department of Biochemistry and Molecular Biology, Monash University, Clayton Campus, Melbourne, Victoria 3800, Australia. Sheena.McGowan@med.monash.edu.au
Oellig
Christine A
CA
Birru
Woldeamanuel A
WA
Caradoc-Davies
Tom T
TT
Stack
Colin M
CM
Lowther
Jonathan
J
Skinner-Adams
Tina
T
Mucha
Artur
A
Kafarski
Pawel
P
Grembecka
Jolanta
J
Trenholme
Katharine R
KR
Buckle
Ashley M
AM
Gardiner
Donald L
DL
Dalton
John P
JP
Whisstock
James C
JC
D000626:Aminopeptidases / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism; D000962:Antimalarials / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D002384:Catalysis; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D015195:Drug Design; D057927:Hydrophobic and Hydrophilic Interactions; D008670:Metals / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D010963:Plasmodium falciparum / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D011485:Protein Binding; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D015800:Protozoan Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism; D013379:Substrate Specificity
D000962:Antimalarials; D008670:Metals; D015800:Protozoan Proteins; D000626:Aminopeptidases