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A MEMBER OF THE NOVEL FIKK FAMILY OF PLASMODIUM FALCIPARUM PUTATIVE PROTEIN KINASES EXHIBITS DIACYLGLYCEROL KINASE ACTIVITY AND IS EXPORTED TO THE HOST ERYTHROCYTE
Title
A MEMBER OF THE NOVEL FIKK FAMILY OF PLASMODIUM FALCIPARUM PUTATIVE PROTEIN KINASES EXHIBITS DIACYLGLYCEROL KINASE ACTIVITY AND IS EXPORTED TO THE HOST ERYTHROCYTE.
Creator
Curtis, David, Chakrabarti, Debopam, University of Central Florida
Abstract / Description
Plasmodium falciparum is one of four species known to cause malaria in humans and is the species that is associated with the most virulent form of the disease. Malaria causes nearly two million deaths each year, many of these occurring among children in under-developed countries of the world. One reason for this is the prevalence of drug resistant strains of malaria that mitigate the efficacy of existing drugs. Hence, the identification of a new generation of pharmacological agents for...
Show morePlasmodium falciparum is one of four species known to cause malaria in humans and is the species that is associated with the most virulent form of the disease. Malaria causes nearly two million deaths each year, many of these occurring among children in under-developed countries of the world. One reason for this is the prevalence of drug resistant strains of malaria that mitigate the efficacy of existing drugs. Hence, the identification of a new generation of pharmacological agents for malaria is extremely urgent. The recent identification of a group of novel protein kinases within the Plasmodium falciparum genome has provided researchers with a basis for what many hope to be new potential drug targets for malaria. Identified within the Plasmodium genome and a few select apicomplexans, these novel proteins have been predicted to be protein kinases based solely on certain sequence features shared with other eukaryotic protein kinases (ePKs). However, to date, no significant studies to determine the function of these novel kinases have been performed. Termed FIKKs, these proteins all possess a non-conserved N-terminal sequence that contains a Plasmodium export element (Pexel) which may target the proteins for export from the parasite and a conserved C-terminal catalytic domain containing a FIKK sequence common to all twenty members of this family. We analyzed the localization of one of the FIKK proteins, FIKK11, encoded by the PF11_0510 locus, during intraerythrocyte differentiation of P. falciparum by Western blot analysis and indirect immunofluorescence assay. Western blot analysis demonstrated that FIKK 11 is expressed within the parasite at all stages of its erythrocytic life cycle with its highest expression occurring during the schizont stage. Immunofluorescence assays showed that this protein is exported from the Plasmodium parasite into the host erythrocyte cytosol which is consistent with studies on other Plasmodium proteins that also have the Pexel motif. To determine the enzymatic activity of FIKK11, we overexpressed the recombinant protein in E. coli and then purified it. However, no protein kinase activity was detected using several commonly used protein kinase substrates including histone H1, myelin basic protein, or dephosphorylated casein. We also did not detect any kinase activity of the native enzyme using pull-down assays of the Plasmodium falciparum cell extract against those same substrates. In addition, kinase substrate peptide array analysis of FIKK11 showed no evidence of protein kinase activity either for FIKK11. Interestingly, however, we were able to detect some kinase activity using the recombinant protein alone with no substrate. The lack of the glycine triad within subdomain I of these FIKK kinases as compared with most traditional eukaryotic protein kinases may explain why we were unable to find any interactions between FIKK11 and other commonly protein kinase substrates. Of interest was the observation that the protein reproducibly exhibited what appeared to be an autophosphorylation activity when using the standard protein kinase assay. Further analyses, however, showed that FIKK11 actually possesses diacylglycerol kinase activity utilizing 1-Stearoyl-2-arachidonoyl-sn-glycerol as a substrate. This is the first evidence of diacylglycerol kinase activity in Plasmodium falciparum. Because FIKK11 is exported into the host cell and is localized on the erythrocyte membrane, its enzymatic activity may potentially have relevance in the pathophysiology of the disease.
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Date Issued
2007
Identifier
CFE0001879, ucf:47407
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0001879
Customer Relationship Marketing by Destination Marketing Organizations: Does it lead to favorable behavioral intentions to meeting planners?
Title
Customer Relationship Marketing by Destination Marketing Organizations: Does it lead to favorable behavioral intentions to meeting planners?.
Creator
Lee, Jumyong, Breiter, Deborah, Wang, Youcheng, Kwun, David, Boote, David, Ro, Hee Jung, Love, Curtis, University of Central Florida
Abstract / Description
In convention market, one of the fastest growing sectors in hospitality industry, meeting planners play an important role to select a destination for their event. Therefore, a good relationship with them can be a competitive advantage for a convention destination considering a fierce competition among the destinations. The objective of this study is to develop an empirically valid relationship marketing (RM) model that would verify the antecedents, mediators, and consequence of the...
Show moreIn convention market, one of the fastest growing sectors in hospitality industry, meeting planners play an important role to select a destination for their event. Therefore, a good relationship with them can be a competitive advantage for a convention destination considering a fierce competition among the destinations. The objective of this study is to develop an empirically valid relationship marketing (RM) model that would verify the antecedents, mediators, and consequence of the relationship between the destination marketing organization (DMO) and meeting planners. This study found three antecedents (i.e., customer orientation, familiarity, and reputation) of the RM mediating constructs that consist of satisfaction, trust, and commitment as well as consequence (i.e. behavioral intention) led by the RM mediators based on review of the literature. Therefore, the hypothesized relationships 1) between the antecedents and the mediators, 2) between the mediators, 3) and 3) between the mediators and the consequence in the model were tested by using structural equation modeling (SEM) with LISREL results. Eight out of eleven hypotheses were supported by the examination of path coefficients while 33 observed indicators were confirmed in the measurement model through confirmatory factor analysis (CFA). The SEM results showed the significant relationships that lead to meaningful implications in both industry and academia while this study is not immune to limitations that can be the starting points of recommendations for future studies.
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Date Issued
2011
Identifier
CFE0004126, ucf:49122
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0004126