title: Metallohistins: a new class of plant metal-binding proteins.
abstract: Two small multimeric histidine-rich proteins, AgNt84 and Ag164, encoded by two nodule-specific cDNAs isolated from nodule cDNA libraries of the actinorhizal host plant Alnus glutinosa, represent a new class of plant metal binding proteins. This paper reports the characterization of the purified in vitro-expressed proteins by size exclusion chromatography, circular dichroism, equilibrium dialysis, metal affinity chromatography coupled with mass spectrometry, and nuclear magnetic resonance spectroscopy. These analyses reveal that each polypeptide is capable of binding multiple atoms of Zn2+, Ni2-, Co2+, Cu2+, Cd2+ and Hg2+. A reversible shift in histidine Cepsilon1 and Cdelta2 protons in NMR analysis occurred during titration of this protein with ZnCl2 strongly suggesting that histidine residues are responsible for metal binding. AgNt84 and Ag164 are not related to metal binding metallothioneins and phytochelatins and represent a new class of plant metal binding proteins that we propose to call metallohistins. Possible biological roles in symbioses for AgNt84 and Ag164, and their potential for use in bioremediation are discussed.
authors.affiliation: Department of Botany, The University of Tennessee, Knoxville, Tennessee 37996, USA.
authors.forename: Rakesh K
authors.initials: RK
authors.lastname: Gupta
authors.forename: Svetlana V
authors.initials: SV
authors.lastname: Dobritsa
authors.forename: Cynthia A
authors.initials: CA
authors.lastname: Stiles
authors.forename: Michael E
authors.initials: ME
authors.lastname: Essington
authors.forename: Zhaoyang
authors.initials: Z
authors.lastname: Liu
authors.forename: Chung-Hsuan
authors.initials: CH
authors.lastname: Chen
authors.forename: Engin H
authors.initials: EH
authors.lastname: Serpersu
authors.forename: Beth C
authors.initials: BC
authors.lastname: Mullin
mesh_terms: D000595:Amino Acid Sequence; D002712:Chlorides / Q000494:pharmacology; D002845:Chromatography; D002942:Circular Dichroism; D018076:DNA, Complementary / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism; D017353:Gene Deletion; D015723:Gene Library; D006639:Histidine / Q000737:chemistry; D017403:In Situ Hybridization; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D008670:Metals / Q000737:chemistry* / Q000145:classification*; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry; D010944:Plants / Q000378:metabolism*; D011506:Proteins / Q000737:chemistry* / Q000145:classification; D017386:Sequence Homology, Amino Acid; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D017967:Zinc Compounds / Q000494:pharmacology; D000099053:Histidine-Rich Glycoprotein
chemical_list: D002712:Chlorides; D018076:DNA, Complementary; D008670:Metals; D010455:Peptides; D011506:Proteins; D017967:Zinc Compounds; D000099053:Histidine-Rich Glycoprotein; D006639:Histidine; C016837:zinc chloride