Disulfide bond assignment, lipid transfer activity and secondary structure of a 7-kDa plant lipid transfer protein, LTP2.
The 7-kDa lipid transfer proteins, LTP2s, share some amino-acid sequence similarities with the 9-kDa isoforms, LTP1s. Both proteins display an identical cysteine motif and, in this regard, LTP2s have been classified as lipid transfer proteins. However, in contrast with LTP1s, no data are available on their structure, cysteine pairings, lipid transfer and lipid binding properties. We reported on the isolation of two isoforms of 7-kDa lipid transfer protein, LTP2, from wheat seeds and showed for the first time that they indeed display lipid transfer activity. Trypsin and chymotrypsin digestions of the native LTP2 afforded the sequence of both isoforms and assignment of disulfide bonds. The cysteine pairings, Cys10--Cys24, Cys25--Cys60, Cys2--Cys34, Cys36--Cys67, revealed a mismatch at the Cys34-X-Cys36 motif of LTP2 compared to LTP1. Moreover, the secondary structure as determined by circular dichroism suggested an identical proportion of alpha helices, beta sheets and random coils. By analogy with the structure of the LTP1, we discussed what structural changes are required to accommodate the LTP2 disulfide pattern.
Laboratoire de Biochimie et Technologie des Protéines, INRA, rue de la Géraudière, Nantes, France. douliez@nantes.inra.fr
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Douliez
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Pato
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Rabesona
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Mollé
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D000595:Amino Acid Sequence; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism*; D002918:Chymotrypsin / Q000378:metabolism; D002942:Circular Dichroism; D003545:Cysteine / Q000378:metabolism; D004220:Disulfides / Q000378:metabolism*; D050556:Fatty Acid-Binding Proteins; D050356:Lipid Metabolism; D008081:Liposomes / Q000378:metabolism; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010940:Plant Proteins / Q000737:chemistry* / Q000378:metabolism*; D020033:Protein Isoforms / Q000737:chemistry / Q000378:metabolism; D017433:Protein Structure, Secondary; D020539:Sequence Analysis, Protein; D014908:Triticum / Q000737:chemistry*; D014357:Trypsin / Q000378:metabolism
D002352:Carrier Proteins; D004220:Disulfides; D050556:Fatty Acid-Binding Proteins; C109356:LTP2 protein, plant; D008081:Liposomes; C422456:Ltp1 protein, barley; D010940:Plant Proteins; D020033:Protein Isoforms; D002918:Chymotrypsin; D014357:Trypsin; D003545:Cysteine