Localisation of the ribosomal proteins L2, L14 and L24 of the E. coli ribosome by means of nuclear spin contrast variation

Ribosomes are ribonucleo-protein complexes, which are the site of the protein synthesis, one of the most important steps during the translation of the genetic code from the DNA to the proteins. The proteins L2, L14 and L24 in the 50S subunit and the protein L2 in the 70S ribosome of the E. coli bacterium were localised by means of nuclear spin contrast variation. The contrast created by isotopic substitution is increased by almost a factor of three provided that polarised neutrons are scattered by polarised hydrogen spins of the sample. To get additional information about the in situ structure of the proteins the shapes were described by a two or three sphere model. Within the project of mapping the 50S subunit of the E. coli ribosome the protein L24 is localised for the first time. L24 is one of the initiator protein for the assembly of the 50S subunit therefore the knowledge of the position is of great interest for the understanding of this process. With the localisation of the protein L14, which is one of the most conserved protein in the ribosome, new hints are given in respect of the protein function which was until now unknown. The localisation of the protein L2, which is one of the candidates of the area of the central step in protein synthesis was done both in the 50S subunit and in the whole 70S ribosome. This allows to investigate conformational changes during the association of the subunits. (orig.)