Protein binding and subunit association activity in particles reconstituted from Escherichia coli MRE600 50S ribosomal components.

Reconstituted 37S and 48S ribonucleoprotein particles were constructed by incubating Escherichia coli ribosomal RNA with total 50S ribosomal proteins by a sequential incubation method. By comparing the protein compositions of the two types of particles, the proteins that bind to 37S complexes to form 48S particles have been determined. Although only 48S particles could associate with 30S subunits, isolated 37S reconstituted particles could do so if incubated with exogenous 50S proteins. The proteins that bind under these conditions and confer upon particles the ability to associate are L2, L11, L15, L18, and L25. The involvement of these proteins in 5S RNA binding is discussed.