Localization of ribosomal proteins on the surface of mammalian 60S ribosomal subunits by means of immobilized enzymes. Correlation with chemical cross-linking data.
Trypsin covalently bound on collagen membranes has been used to investigate the protein topography in eukaryotic 60S ribosomal subunits. Six proteins are highly exposed to the attack of the immobilized enzyme: L6, L7-L7a, L17, L24, and L31. They are located in two distinct regions, forming two bulges at the ribosomal surface; the first one consists of proteins L6 and L7-L7a, which are screening proteins degraded later, as L4, L14, L23a, and L29; the second one is formed by proteins L17, L24, and L31, which are shielding L19 and L22. L3, L5, L8, L11, L12, L26, L30, L34, and L37a, are located in a trough between the two bulges. L10, close to L5, appears to be more accessible than all these proteins. Several proteins are not degraded by trypsin, even for a very long time of incubation: L9, L13-L13a, L18, L18a, L21, L25, L27-L27a, L28, L32, L35, L35a, L36-L36a, and L38. The cross-linking data suggest that these latter proteins are mainly protected by the proteins located in the L6-L7-L7a region, and by the 28S RNA. A model of protein topography within the 60S rat liver subunits, based on protein accessibility and cross-linking data, is proposed.
Laboratoire de Biologie et Technologie des Membranes, C.N.R.S. UM 24 Université Claude Bernard de Lyon, Villeurbanne, France.
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D000818:Animals; D003094:Collagen; D003432:Cross-Linking Reagents / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D006868:Hydrolysis; D008954:Models, Biological; D051381:Rats; D012269:Ribosomal Proteins / Q000032:analysis*; D012270:Ribosomes / Q000032:analysis / Q000187:drug effects / Q000648:ultrastructure*; D014357:Trypsin / Q000378:metabolism
D003432:Cross-Linking Reagents; D012269:Ribosomal Proteins; D003094:Collagen; D014357:Trypsin