The low-molecular-mass rhoptry complex of Plasmodium falciparum consists of three proteins, rhoptry-associated protein 1 (RAP1), RAP2, and RAP3. The genes encoding RAP1 and RAP2 are known; however, the RAP3 gene has not been identified. In this study we identify the RAP3 gene from the P. falciparum genome database and show that this protein is part of the low-molecular-mass rhoptry complex. Dis...

The PyAG1 gene, identified by the screening of a Plasmodium yoelii genomic DNA library with a rhoptry-specific Mab, encodes a protein with a zinc finger structure immediately followed by the consensus sequence of the Arf GAP catalytic site. The serum of mice immunized with the recombinant protein recognized specifically the rhoptries of the late infected erythrocytic stages. Blast analysis usin...

Rho family small GTPases are signaling switches controlling many eukaryotic cellular processes. Conversion from the GDPto GTP-bound form is catalyzed by guanine nucleotide exchange factors (GEFs). Rho GEFs in animals fall into two structurally distinct classes containing DH and DOCKER catalytic domains. Using a plant Rho GTPase (ROP1) as bait in yeast two-hybrid screens, we identified a family ...

The human malaria parasite Plasmodium falciparum possesses sophisticated systems of protein secretion to modulate host cell invasion and remodeling. In the present study, we provide insights into the function of the AP-1 complex in P. falciparum. We utilized GFP fusion constructs for live cell imaging, as well as fixed parasites in immunofluorescence analysis, to study adaptor protein mu1 (Pfμ1...

Rho family small GTPases are universal signaling switches in the control of cell polarity in eukaryotic cells. Their polar distribution to the cell cortex is critical for the execution of their functions, yet the mechanism for this distribution is poorly understood. Using a yeast two-hybrid method, we identified RIP1 (ROP interactive partner 1), which belongs to a family of five members of nove...

A competitive-inhibition enzyme-linked immunosorbent assay (cELISA) was developed for detection of equine antibodies specific for Babesia caballi. The assay used recombinant B. caballi rhoptry-associated protein 1 (RAP-1) and monoclonal antibody (MAb) 79/17.18.5, which is reactive with a peptide epitope of a native 60-kDa B. caballi antigen. The gene encoding the recombinant antigen was sequenc...

Biological oscillation occurs at various levels, from cellular signaling to organismal behaviors. Mathematical modeling has allowed a quantitative understanding of slow oscillators requiring changes in gene expression (e.g., circadian rhythms), but few theoretical studies have focused on the rapid oscillation of cellular signaling. The tobacco pollen tube, which exhibits growth bursts every 80 ...

Eukaryotic Armadillo (ARM) repeat proteins are multifaceted with prominent roles in cell-cell adhesion, cytoskeletal regulation and intracellular signaling among many others. One such ARM repeat containing protein, ARM Repeats Only (ARO), has recently been demonstrated in both Toxoplasma (TgARO) and Plasmodium (PfARO) parasites to be targeted to the rhoptries during the late asexual stages. TgA...

Oscillation regulates a wide variety of processes ranging from chemotaxis in Dictyostelium through segmentation in vertebrate development to circadian rhythms. Most studies on the molecular mechanisms underlying oscillation have focused on processes requiring a rhythmic change in gene expression, which usually exhibit a periodicity of >10 min. Mechanisms that control oscillation with shorter pe...