title: eEF1A isoforms change in abundance and actin-binding activity during maize endosperm development.
abstract: Eukaryotic elongation factor 1A (eEF1A) appears to be a multifunctional protein because several biochemical activities have been described for this protein, in addition to its role in protein synthesis. In maize (Zea mays) endosperm, the synthesis of eEF1A is increased in o2 (opaque2) mutants, and its concentration is highly correlated with the protein-bound lysine content. To understand the basis of this relationship, we purified eEF1A isoforms from developing endosperm and investigated their accumulation and their functional and structural properties. Formation of three isoforms appears to be developmentally regulated and independent of the o2 mutation, although one isoform predominated in one high lysine o2 inbred. The purified proteins differ in their ability to bind F-actin in vitro, suggesting that they are functionally distinct. However, they share similar aminoacyl-tRNA-binding activities. Tandem mass spectrometry revealed that each isoform is composed of the four same gene products, which are modified posttranslationally by methylation and phosphorylation. The chemical differences that account for their different actin-binding activities could not be determined.
authors.affiliation: Department of Plant Sciences, University of Arizona, Tucson, Arizona 85721, USA.
authors.forename: Jose A
authors.initials: JA
authors.lastname: Lopez-Valenzuela
authors.forename: Bryan C
authors.initials: BC
authors.lastname: Gibbon
authors.forename: Peter A
authors.initials: PA
authors.lastname: Hughes
authors.forename: Theo W
authors.initials: TW
authors.lastname: Dreher
authors.forename: Brian A
authors.initials: BA
authors.lastname: Larkins
mesh_terms: D000199:Actins / Q000378:metabolism*; D000595:Amino Acid Sequence; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D009154:Mutation; D020648:Peptide Elongation Factor 1 / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D011485:Protein Binding; D020033:Protein Isoforms / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D012346:RNA, Transfer, Amino Acyl / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012639:Seeds / Q000254:growth & development* / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D003313:Zea mays / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism
chemical_list: D000199:Actins; D020648:Peptide Elongation Factor 1; D020033:Protein Isoforms; D012346:RNA, Transfer, Amino Acyl