Chapter 21

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Gildas Bourdais, Dominique Job, and Philippe Grappin. Abstract. The: form:.nion of abnormal isoaspanyl residuc:s ckr,,'ed from aspartyl or asparaginyl residw:s ...
Chapter 21 Proteln Damage and Repalr Controlllng Seed VIgor and Longevtty Laurent Ogé, Caroline Broyart, Boris Collet, Béatrice Godin, Denis Jallet, Gildas Bourdais, Dominique Job, and Philippe Grappin Abstract The: form:.nion of a bno rmal isoaspanyl residuc:s ckr,,'ed from aspartyl or asparaginyl residw:s is a major source of spontanc:ous prote: in misfolding in cc: Ils. The: re: pair enzyme prote in L·isoospartyl methyltr.lJlS. fc:rasc: ( PI.MT) counteracts such damage: by catalyzing the con,·c:rsion of abnormal isoasp.ut)•l residues to the ir nonnal aspart)•l forms. Thus, this enzyme: conributes to the survival of m3Jly organisms, including plants. Analysis of the accumulation o f iso.tspartyl·c·:mtai.ni.ng protc:ins and its modulation by the: Pll\.IT rc:pair path\\'3)\ using germination tests, immunodc:tc:ccion, eru:ymacic assays, and HPLC anaJysis, givc:s new insi.gbts in undc:rstandi.ng controlling mc:chanisms of sc:c:d longc:vity and \i.gor. Key w ordo1 l 11o.v.:partyl m\"thyl~erau, Arobidop11~, Seed , Longevity, Vigor

1. Introduction Undcr physiological conditions) cellular protcins arc subjcctcd to noncnzymatic isomcrization andjor dcamidation of aspartyi and asparaginyt residues) rcspcctivcly. Thcse spont:aneous reactions give risc to the fonnation of an abnormal isoaspartyl rcsidue via a succinimide intermcdiate (cyclic imide) ( 1). This damage can affect the physicochemical properties and bio logical activity of pro teins (2, 3 ) sincc the peptide backbone is rran.sferrcd from the alpha· carboxyl group to the side·chain bcta·carboX)i (Fig. 1). Protein L·isoaspartyl methyltransferasc (PIMT; EC 2.1.1.77) is a lùghly conscrvcd enzyme that can specifically recognizc protcins conraining altercd aspartyl rcsiducs. PIMT catalyzcs the transfi:r of a methyl group from S·ade nosyl metlùonine (AdoMet) to the free

Allieon R. Kermode (ed.). &Md Darnw7cr; Methode Sfld A'oltlects. Method& in Molecular Biology. vol. rn. Da 1 0.1007/97~ 1-81 n&-231-1..21 .0 ~ringerScienoe+Bueineee Meda. LLC201 1

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