Erythromycin binds to the 50S subunit (which is the larger part of a
ribosome) and inhibits
translocation in
prokaryotes.
In other words: this macrolide (meaning: containing a macrocyclic
lactone
ring)
antibiotic prevents
bacteria from making
proteins by preventing
the
molecule carrying the aminoacid (
tRNA) to connect to the mRNA chain.