title: Analysis of EF-hand-containing proteins in Arabidopsis.
abstract: BACKGROUND
  In plants, calcium (Ca2+) has emerged as an important messenger mediating the action of many hormonal and environmental signals, including biotic and abiotic stresses. Many different signals raise cytosolic calcium concentration ([Ca2+]cyt), which in turn is thought to regulate cellular and developmental processes via Ca2+-binding proteins. Three out of the four classes of Ca2+-binding proteins in plants contain Ca2+-binding EF-hand motif(s). This motif is a conserved helix-loop-helix structure that can bind a single Ca2+ ion. To identify all EF-hand-containing proteins in Arabidopsis, we analyzed its completed genome sequence for genes encoding EF-hand-containing proteins.
  
  
  RESULTS
  A maximum of 250 proteins possibly having EF-hands were identified. Diverse proteins, including enzymes, proteins involved in transcription and translation, protein- and nucleic-acid-binding proteins and a large number of unknown proteins, have one or more putative EF-hands. Phylogenetic analysis identified six major groups that contain some families of proteins.
  
  
  CONCLUSIONS
  The presence of EF-hand motif(s) in a diversity of proteins is consistent with the involvement of Ca2+ in regulating many cellular and developmental processes. Thus far, only 47 of the possible 250 EF-hand proteins have been reported in the literature. Various domains that we identified in many of the uncharacterized EF-hand-containing proteins should help in elucidating their cellular role(s). Our analyses suggest that the Ca2+ messenger system is widely used in plants and that EF-hand-containing proteins are likely to be the key transducers mediating Ca2+ action.
authors.affiliation: Department of Biology and Program in Cell and Molecular Biology, Colorado State University, Fort Collins, CO 80523, USA.
authors.forename: Irene S
authors.initials: IS
authors.lastname: Day
authors.forename: Vaka S
authors.initials: VS
authors.lastname: Reddy
authors.forename: Gul
authors.initials: G
authors.lastname: Shad Ali
authors.forename: A S N
authors.initials: AS
authors.lastname: Reddy
mesh_terms: D017360:Arabidopsis / Q000737:chemistry* / Q000235:genetics; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000235:genetics; D002135:Calcium-Binding Proteins / Q000737:chemistry / Q000235:genetics; D030562:Databases, Protein; D020832:EF Hand Motifs / Q000235:genetics; D010802:Phylogeny; D021382:Protein Sorting Signals / Q000235:genetics; D017434:Protein Structure, Tertiary / Q000235:genetics; D020539:Sequence Analysis, Protein / Q000379:methods*
chemical_list: D029681:Arabidopsis Proteins; D002135:Calcium-Binding Proteins; D021382:Protein Sorting Signals