rRNA (Ribosomal ribonucleic acid) is the RNA part of the ribosome, the cell structure which is the site of protein synthesis in all living cells. The Ribosomal RNA provides a mechanism for decoding mRNA into amino acids and interacts with tRNAs during translation by giving peptidyl transferase activity. The tRNAs bring the must amino acids corresponding to the appropriate mRNA codon. The ribosomal RNAs begin two subunits the LSU (large subunit) and SSU (small subunit). mRNA is sandwiched between the large and small subunits and the ribosome catalyzes the formation of a peptide bond between the 2 amino acids which are included in the rRNA.