Structure and function of a mitochondrial late embryogenesis abundant protein are revealed by desiccation.
Few organisms are able to withstand desiccation stress; however, desiccation tolerance is widespread among plant seeds. Survival without water relies on an array of mechanisms, including the accumulation of stress proteins such as the late embryogenesis abundant (LEA) proteins. These hydrophilic proteins are prominent in plant seeds but also found in desiccation-tolerant organisms. In spite of many theories and observations, LEA protein function remains unclear. Here, we show that LEAM, a mitochondrial LEA protein expressed in seeds, is a natively unfolded protein, which reversibly folds into alpha-helices upon desiccation. Structural modeling revealed an analogy with class A amphipathic helices of apolipoproteins that coat low-density lipoprotein particles in mammals. LEAM appears spontaneously modified by deamidation and oxidation of several residues that contribute to its structural features. LEAM interacts with membranes in the dry state and protects liposomes subjected to drying. The overall results provide strong evidence that LEAM protects the inner mitochondrial membrane during desiccation. According to sequence analyses of several homologous proteins from various desiccation-tolerant organisms, a similar protection mechanism likely acts with other types of cellular membranes.
Tolleter
Dimitri
D
Unité Mixte de Recherche 1191, Physiologie Moléculaire des Semences, Université d'Angers/Institut National d'Horticulture/Institut National de la Recherche Agronomique, Angers F-49045, France.
Jaquinod
Michel
M
Mangavel
Cécile
C
Passirani
Catherine
C
Saulnier
Patrick
P
Manon
Stephen
S
Teyssier
Emeline
E
Payet
Nicole
N
Avelange-Macherel
Marie-Hélène
MH
Macherel
David
D
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics; D002942:Circular Dichroism; D003890:Desiccation; D008081:Liposomes / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D018532:Pisum sativum / Q000737:chemistry*; D010743:Phospholipids / Q000378:metabolism; D010940:Plant Proteins / Q000737:chemistry* / Q000378:metabolism*; D030821:Plants, Genetically Modified; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017550:Spectroscopy, Fourier Transform Infrared; D013329:Structure-Activity Relationship
D008081:Liposomes; D024101:Mitochondrial Proteins; D010743:Phospholipids; D010940:Plant Proteins; C066246:late embryogenesis abundant protein, plant