Actin-related proteins (Arps) constitute a family of eukaryotic cytoskeletal proteins involved in such diverse events as cell motility, cytokinesis, vesicle transport, and chromatin remodelling. Previously, in a study of Plasmodium berghei gene expression in ookinetes and oocysts, we detected stage-specific increased expression of a gene encoding an Arp. Here we further characterize this gene and

We report two crystal structures of the PARP domain of human tankyrase-2 (TNKS2). Tankyrases are involved in fundamental cellular processes such as telomere homeostasis and Wnt signaling. The complex of TNKS2 with the potent inhibitor XAV939 provides insights into the molecular basis of the strong interaction and suggests routes for further development of tankyrase inhibitors.

RNA helicases of the DExD/H-box superfamily are critically involved in all RNA-related processes. No crystal structures of human DExH-box domains had been determined previously, and their structures were difficult to predict owing to the low level of homology among DExH-motif-containing proteins from diverse species. Here we present the crystal structures of the conserved domain 1 of the DEIH-moti

The malaria parasite Plasmodium depends on its actin-based motor system for motility and host-cell invasion. Actin-depolymerization factors are important regulatory proteins that affect the rate of actin turnover. Plasmodium has two actin-depolymerization factors which seem to have different functions and display low sequence homology to the higher eukaryotic family members. Plasmodium actin-depol

ADP-ribosylation is a post-translational modification of proteins catalyzed by ADP-ribosyltransferases. It comprises the transfer of the ADP-ribose moiety from NAD+ to specific amino acid residues on substrate proteins or to ADP-ribose itself. Currently, 22 human genes encoding proteins that possess an ADP-ribosyltransferase catalytic domain are known. Recent structural and enzymological evidence

Poly-ADP-ribose polymerases (PARPs) catalyze transfer of ADP-ribose from NAD(+) to specific residues in their substrate proteins or to growing ADP-ribose chains. PARP activity is involved in processes such as chromatin remodeling, transcription control, and DNA repair. Inhibitors of PARP activity may be useful in cancer therapy. PARP2 is the family member that is most similar to PARP1, and the two

Cyclase-associated proteins (CAPs) are evolutionary conserved G-actin-binding proteins that regulate microfilament turnover. CAPs have a modular structure consisting of an N-terminal adenylate cyclase binding domain, a central proline-rich segment, and a C-terminal actin binding domain. Protozoan parasites of the phylum Apicomplexa, such as Cryptosporidium and the malaria parasite Plasmodium, expr

The 70-kDa heat shock proteins (Hsp70) are chaperones with central roles in processes that involve polypeptide remodeling events. Hsp70 proteins consist of two major functional domains: an N-terminal nucleotide binding domain (NBD) with ATPase activity, and a C-terminal substrate binding domain (SBD). We present the first crystal structures of four human Hsp70 isoforms, those of the NBDs of HSPA1L

The PARP-3 protein is closely related to the PARP-1 and PARP-2 proteins, which are involved in DNA repair and genome maintenance. Here, we characterized the biochemical properties of human PARP-3. PARP-3 is able to ADP-ribosylate itself as well as histone H1, a previously unknown substrate for PARP-3. PARP-3 is not activated upon binding to DNA and is a mono-ADP-ribosylase, in contrast to PARP-1 a

Paraplegin is an m-AAA protease of the mitochondrial inner membrane that is linked to hereditary spastic paraplegias. The gene encodes an FtsH-homology protease domain in tandem with an AAA+ homology ATPase domain. The protein is believed to form a hexamer that uses ATPase-driven conformational changes in its AAA-domain to deliver substrate peptides to its protease domain. We present the crystal s

Summary Successful malaria transmission from the mosquito vector to the mammalian host depends crucially on active sporozoite motility. Sporozoite locomotion and host cell invasion are driven by the parasite's own actin/myosin motor. A unique feature of this motor machinery is the presence of very short subpellicular actin filaments. Therefore, F-actin stabilizing proteins likely play a central ro

Poly(ADP-ribose) polymerases (PARPs) activate DNA repair mechanisms upon stress- and cytotoxin-induced DNA damage, and inhibition of PARP activity is a lead in cancer drug therapy. We present a structural and functional analysis of the PARP domain of human PARP-3 in complex with several inhibitors. Of these, KU0058948 is the strongest inhibitor of PARP-3 activity. The presented crystal structures

DEXD/H-box RNA helicases couple ATP hydrolysis to RNA remodeling by an unknown mechanism. We used x-ray crystallography and biochemical analysis of the human DEXD/H-box protein DDX19 to investigate its regulatory mechanism. The crystal structures of DDX19, in its RNA-bound prehydrolysis and free posthydrolysis state, reveal an alpha-helix that inserts between the conserved domains of the free prot

Profilins are key regulators of actin dynamics. They sequester actin monomers, forming a pool for rapid polymer formation stimulated by proteins such as formins. Apicomplexan parasites utilize a highly specialized microfilament system for motility and host cell invasion. Their genomes encode only a small number of divergent actin regulators. We present the first crystal structure of an apicomplexa

Iba2 is a homolog of ionized calcium-binding adapter molecule 1 (Iba1), a 17-kDa protein that binds and cross-links filamentous actin (F-actin) and localizes to membrane ruffles and phagocytic cups. Here, we present the crystal structure of human Iba2 and its homodimerization properties, F-actin cross-linking activity, cellular localization and recruitment upon bacterial invasion in comparison wit

Spinophilin, a neuronal scaffolding protein, is essential for synaptic transmission, and functions to target protein phosphatase-1 to distinct subcellular locations in dendritic spines. It is vital for the regulation of dendritic spine formation and motility, and functions by regulating glutamatergic receptors and binding to filamentous actin. To investigate its role in regulating actin cytoskelet

Inosine triphosphatase (ITPA) is a ubiquitous key regulator of cellular non-canonical nucleotide levels. It breaks down inosine and xanthine nucleotides generated by deamination of purine bases. Its enzymatic action prevents accumulation of ITP and reduces the risk of incorporation of potentially mutagenic inosine nucleotides into nucleic acids. Here we describe the crystal structure of human ITPA

10-Formyltetrahydrofolate dehydrogenase is a ubiquitously expressed enzyme in the human body. It catalyses the formation of tetrahydrofolate and carbon dioxide from 10-formyltetrahydrofolate, thereby playing an important role in the human metabolism of one-carbon units. It is a two-domain protein in which the N-terminal domain hydrolyses 10-formyltetrahydrofolate into formate and tetrahydrofolate.

Efficient and rapid host cell invasion is a prerequisite for an intracellular parasitic life style. Pathogens typically induce receptor-mediated endocytosis and hijack the force-transducing system of a host cell to gain access to a replication-competent niche. In striking contrast, apicomplexan parasites such as Plasmodium, the causative agent of malaria, and the human and animal pathogens Toxopla