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Kessler, Félix

Nom
Kessler, Félix
Affiliation principale
Fonction
Professeur.e ordinaire
Email
felix.kessler@unine.ch
Identifiants
https://libra.unine.ch/handle/123456789/320
_
0000-0001-6409-5043

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  • Publication
    Métadonnées seulement
    Identification of proteins associated with plastoglobules isolated from pea (Pisum sativum L.) chloroplasts
    (1999)
    Kessler, Félix 
    ;
    Schnell, Danny
    ;
    Blobel, Gunter
    Plastoglobules are conspicuous lipid-containing structures in the chloroplast stroma and are thought to serve as lipid reservoirs for thylakoid membranes. Plastoglobules also contain low levels of proteins. We have purified plastoglobules from a pea chloroplast membrane fraction. Sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis of the purified plastoglobules revealed more than a dozen distinct polypeptides that we propose to term plastoglobulins. For one of the proteins, termed plastoglobulin 1 (PG1), we have obtained partial N-terminal and internal protein sequences. The amino acid sequence, deduced from cDNA, encoded a precursor protein of a calculated mass of 38,491 Da which contained a 48-residue-long N-terminal signal sequence. Pre-PG1 obtained by coupled in-vitro transcription/translation was imported into pea chloroplasts, its signal sequence was cleaved and mature PG1 was assembled into plastoglobules. Homology searches of the data bases revealed similarity of PG1 to the plastoglobule-associated protein of Capsicum annuum, the carotenoid-associated protein of Cucumis sativus and to a protein of the cyanobacterium Synechocystis sp., indicating that PG1 is a novel member of an ancient protein family. Immunoelectron microscopy using PG1-specific antibodies indicated that PG1 is present in multiple copies on the surface of plastoglobules.
  • Publication
    Métadonnées seulement
    A consensus nomenclature for the protein-import components of the chloroplast envelope
    (1997)
    Schnell, Danny
    ;
    Blobel, Gunter
    ;
    Keegstra, Kenneth
    ;
    Kessler, Félix 
    ;
    Ko, Kenton
    ;
    Soll, Jurgen
  • Publication
    Métadonnées seulement
    Interaction of the protein import and folding machineries in the chloroplast
    (1996)
    Kessler, Félix 
    ;
    Blobel, Gunter
    We report the molecular cloning of import intermediate associated protein (IAP) 100, a 100-kDa protein of the chloroplast protein import machinery of peas, IAP100 contains two potential alpha-helical transmembrane segments and also behaves like an integral membrane protein, It was localized to the inner chloroplast envelope membrane, Immunoprecipitation experiments using monospecific anti-IAP100 antibodies and a nonionic detergent-generated chloroplast lysate gave the following results, (i) The four integral membrane proteins of the outer chloroplast import machinery were not coprecipitated with IAP100 indicating that the inner and outer membrane import machineries are not coupled in isolated chloroplasts. (ii) the major protein that coprecipitated with IAP100 was identified as stromal chaperonin 60 (cpn60); the association of IAP100 and cpn60 was specific and was abolished when immunoprecipitation vias carried out in the presence of ATP, (iii) In a lysate from chloroplasts that had been preincubated for various lengths of time in an import reaction with radiolabeled precursor (pS) of the small subunit of Rubisco, we detected coimmunoprecipitation of IAP100, cpn60, and the imported mature form (S) of precursor, Relative to the time course of import, coprecipitation of S first increased and then decreased, consistent with a transient association of the newly imported S with the chaperonin bound to IAP100. These data suggest that IAP100 serves in recruiting chaperonin for folding of newly imported proteins.
  • Publication
    Métadonnées seulement
    Isolation of components of the chloroplast protein import machinery
    (1994)
    Schnell, Danny
    ;
    Kessler, Félix 
    ;
    Blobel, Gunter
    Components of the protein import machinery of the chloroplast were isolated by a procedure in which the import machinery was engaged in vitro with a tagged import substrate under conditions that yielded largely chloroplast envelope-bound import intermediates. Subsequent detergent solubilization of envelope membranes showed that six envelope polypeptides copurified specifically and, apparently, stoichiometrically with the import intermediates. Four of these polypeptides are components of the outer membrane import machinery and are associated with early import intermediates. Two of these polypeptides have been characterized. One is a homolog of the heat shock protein hsp70; the other one is a channel-protein candidate.
  • Publication
    Métadonnées seulement
    Identification of two gtp-binding proteins in the chloroplast protein import machinery
    (1994)
    Kessler, Félix 
    ;
    Blobel, Gunter
    ;
    Patel, Hitesh A
    ;
    Schnell, Danny
    Two of four proteins that associated with translocation intermediates during protein import across the outer chloroplast envelope membrane were identified as guanosine triphosphate (GTP)-binding proteins. Both proteins are integral membrane proteins of the outer chloroplast membrane, and both are partially exposed on the chloroplast surface where they were accessible to thermolysin digestion. Engagement of the outer membrane's import machinery by an import substrate was inhibited by slowly hydrolyzable or non-hydrolyzable GTP analogs. Thus, these GTP-binding proteins may function in protein import into chloroplasts.