title: Calmodulin expression during Giardia intestinalis differentiation and identification of calmodulin-binding proteins during the trophozoite stage.
abstract: Calmodulin (CaM) is the primary sensor for calcium in the cell. It modulates various functions by activating CaM-binding proteins (CaMBPs). This study examined the calcium/CaM-dependent system in the ancient eukaryote Giardia intestinalis. A specific antibody against the parasite's CaM was developed; this protein's expression and location during different stages of the parasite's life cycle were analyzed. The results showed that it is a housekeeping protein which is possibly involved in the parasite's motility. No CaMBP has been identified in G. intestinalis to date. Pull-down assays were used for isolating proteins which specifically bind to CaM in a calcium-dependent way. Three of them were identified through mass spectrometry; they were GASP180, α-tubulin, and pyruvate phosphate dikinase (PPDK).The first two are cytoskeleton proteins, and the last one is an essential enzyme for glycolysis. The presence of binding sites was analyzed through bioinformatics in each protein sequence. This is the first report of a CaMBP in this organism; it is considered to be a very interesting differentiation model, indicating that CaM is involved at least in two vital processes: G. intestinalis motility and energetic metabolism.
authors.affiliation: Biochemistry Basic Research Laboratory, Chemistry Department, Science Faculty, Universidad Nacional de Colombia, Calle 44, No 45-67, Bloque 10, nivel 4, Unidad Camilo Torres, Bogotá, Colombia.
authors.forename: Magda E
authors.initials: ME
authors.lastname: Alvarado
authors.forename: Moisés
authors.initials: M
authors.lastname: Wasserman
mesh_terms: D002118:Calcium / Q000378:metabolism; D002147:Calmodulin / Q000235:genetics / Q000378:metabolism*; D002148:Calmodulin-Binding Proteins / Q000378:metabolism*; D018929:Cell Culture Techniques; D002454:Cell Differentiation; D002465:Cell Movement; D019295:Computational Biology; D016829:Giardia lamblia / Q000254:growth & development* / Q000378:metabolism; D010802:Phylogeny; D011499:Protein Processing, Post-Translational; D015800:Protozoan Proteins / Q000378:metabolism*; D011772:Pyruvate, Orthophosphate Dikinase / Q000378:metabolism; D053058:Trophozoites / Q000378:metabolism*; D014404:Tubulin
chemical_list: D002147:Calmodulin; D002148:Calmodulin-Binding Proteins; D015800:Protozoan Proteins; D014404:Tubulin; D011772:Pyruvate, Orthophosphate Dikinase; D002118:Calcium