Biochemical characterization of a truncated penta-EF-hand Ca2+ binding protein from maize.
Plants possess multiple genes encoding calcium sensor proteins that are members of the penta-EF-hand (PEF) family. Characterized PEF proteins such as ALG-2 (apoptosis-linked gene 2 product) and the calpain small subunit function in diverse cellular processes in a calcium-dependent manner by interacting with their target proteins at either their N-terminal extension or Ca2+ binding domains. We have identified a previously unreported class of PEF proteins in plants that are notable because they do not possess the hydrophobic amino acid rich N-terminal extension that is typical of these PEF proteins. We demonstrate that the maize PEF protein without the N-terminal extension has the characteristics of known PEF proteins; the protein binds calcium in the 100 nM range and, as a result of calcium binding, displays an increase in hydrophobicity. Characterization of the truncated maize PEF protein provides insights into the role of the N-terminal extension in PEF protein signaling. In the context of the current model of how PEF proteins are activated by calcium binding, these results demonstrate that this distinctive class of PEF proteins could function as calcium sensor proteins in plants even in the absence of the N-terminal extension.
Barry
Jennifer K
JK
Pioneer Hi-Bred International, A DuPont Company, 7300 NW 62nd Avenue, Johnston, Iowa 50131, USA.
Selinger
David A
DA
Wang
Cunxi
C
Olsen
Odd-Arne
OA
Rao
A Gururaj
AG
D000595:Amino Acid Sequence; D002118:Calcium / Q000737:chemistry*; D002135:Calcium-Binding Proteins / Q000737:chemistry* / Q000145:classification / Q000235:genetics; D002413:Cations, Divalent / Q000737:chemistry; D008969:Molecular Sequence Data; D010802:Phylogeny; D010940:Plant Proteins / Q000737:chemistry* / Q000145:classification / Q000235:genetics; D011487:Protein Conformation; D020539:Sequence Analysis, Protein; D017384:Sequence Deletion; D014364:Tryptophan / Q000737:chemistry; D003313:Zea mays / Q000378:metabolism*
D002135:Calcium-Binding Proteins; D002413:Cations, Divalent; D010940:Plant Proteins; D014364:Tryptophan; D002118:Calcium