title: Structural characterization of a novel Ca2+-binding protein from Entamoeba histolytica: structural basis for the observed functional differences with its isoform.
abstract: A novel Ca(2+)-binding protein (EhCaBP2) was identified from the protozoan parasite Entamoeba histolytica. EhCaBP2 has 79% sequence identity with calcium-binding protein EhCaBP1. The 3D structure of EhCaBP2 was determined using multidimensional nuclear magnetic resonance spectroscopic techniques. The study reveals that the protein consists of two globular domains connected by a short flexible linker region of four residues. On comparison of the 3D structure and dynamics of EhCaBP2 with those of EhCaBP1, it is found that they vary significantly in their N-terminal domains and interdomain linker. Immunofluorescence localization experiments revealed that EhCaBP1 and EhCaBP2 may not carry out similar functions, as their cellular distribution patterns are not the same. The functional differences between the two isoforms are explained on the basis of results obtained from the structural studies. The structural variation in the interdomain linker region and the formation of functionally important hydrophobic clefts in different regions of EhCaBP1 and EhCaBP2 provide interesting insights into the differences in the functionality of these two isoforms.
authors.affiliation: Department of Chemical Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai, 400005, India. sourajit1@gmail.com
authors.forename: Sourajit Mitra
authors.initials: SM
authors.lastname: Mustafi
authors.forename: Ritu Bansal
authors.initials: RB
authors.lastname: Mutalik
authors.forename: Ruchi
authors.initials: R
authors.lastname: Jain
authors.forename: Kousik
authors.initials: K
authors.lastname: Chandra
authors.forename: Alok
authors.initials: A
authors.lastname: Bhattacharya
authors.forename: Kandala V R
authors.initials: KV
authors.lastname: Chary
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002135:Calcium-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D004748:Entamoeba histolytica / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D020033:Protein Isoforms / Q000737:chemistry / Q000378:metabolism; D017434:Protein Structure, Tertiary
chemical_list: D002135:Calcium-Binding Proteins; D020033:Protein Isoforms; C085578:Ca-binding protein 2; C085577:Ca2+-binding protein-1