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From Proteopedia
Crystal structure of apo carboxy cGMP binding domain of Plasmodium falciparum PKG
Structural highlights
FunctionKGP_PLAF7 Serine/threonine protein kinase which acts as a downstream effector of the second messenger cGMP (PubMed:12068803, PubMed:12817987, PubMed:26149123). Controls the release of Ca(2+) from intracellular stores by regulating phosphoinositide biosynthesis (PubMed:24594931). Ca(2+) signals are essential for merozoite and sporozoite invasion and egress from host hepatocytes and erythrocytes, and, in the mosquito vector, for gametocyte activation, and ookinete and sporozoite motility (PubMed:24594931). During the host liver stage, regulates the initial invasion of host hepatocytes by sporozoites by regulating sporozoite motility and microneme exocytosis (By similarity). Following parasite development in the hepatocytes, required for the release of merosomes, a vesicle containing the mature merozoites (By similarity). During the asexual blood stage, required for the progression from schizont to the ring stage following merozoite invasion of host erythrocytes and for merozoite egress (PubMed:19915077, PubMed:26149123, PubMed:25646845). Regulates merozoite egress by promoting the release of exonemes and micronemes which contain proteins essential for egress (PubMed:23675297). Phosphorylates CDPK1 predominantly at the late schizont stage; phosphorylation at 'Ser-64' regulates CDPK1 protein-protein interaction and phosphorylation at 'Thr-231' may regulate CDPK1 kinase activity (PubMed:26149123). Phosphorylates MyoA at 'Ser-19' (PubMed:26149123). In the mosquito vector, required for the initiation of gametogenesis induced by xanthurenic acid, specifically the gametocyte differentiation from the crescent-shaped form to the spherical form (PubMed:18532880). Required for the gliding motility of ookinetes to reach and penetrate the midgut epithelium by promoting Ca(2+)-mediated activation of CDPK1 and CDPK4 (By similarity). Also required for microneme secretion in ookinete by promoting Ca(2+)-mediated activation of CDPK3 (By similarity).[UniProtKB:A0A509AKL0][1] [2] [3] [4] [5] [6] [7] [8] Publication Abstract from PubMedThe Plasmodium falciparum cGMP-dependent protein kinase (PfPKG) is a key regulator across the malaria parasite life cycle. Little is known about PfPKG's activation mechanism. Here we report that the carboxyl cyclic nucleotide binding domain functions as a "gatekeeper" for activation by providing the highest cGMP affinity and selectivity. To understand the mechanism, we have solved its crystal structures with and without cGMP at 2.0 and 1.9 A, respectively. These structures revealed a PfPKG-specific capping triad that forms upon cGMP binding, and disrupting the triad reduces kinase activity by 90%. Furthermore, mutating these residues in the parasite prevents blood stage merozoite egress, confirming the essential nature of the triad in the parasite. We propose a mechanism of activation where cGMP binding allosterically triggers the conformational change at the alphaC-helix, which bridges the regulatory and catalytic domains, causing the capping triad to form and stabilize the active conformation. Crystal Structures of the Carboxyl cGMP Binding Domain of the Plasmodium falciparum cGMP-dependent Protein Kinase Reveal a Novel Capping Triad Crucial for Merozoite Egress.,Kim JJ, Flueck C, Franz E, Sanabria-Figueroa E, Thompson E, Lorenz R, Bertinetti D, Baker DA, Herberg FW, Kim C PLoS Pathog. 2015 Feb 3;11(2):e1004639. doi: 10.1371/journal.ppat.1004639., eCollection 2015 Feb. PMID:25646845[9] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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