The E. coliribosomal S15 leader is an RNA element that can form two alternative structures found in the ribosomal S15 protein. One of the two alternate structures is a series of three hairpins, the other includes a pseudoknot. This structure causes translational regulation of the S15 protein. Only the final two hairpins are conserved in other species.
^Benard, L; Philippe C; Ehresmann B; Ehresmann C; Portier C (1996). "Pseudoknot and translational control in the expression of the S15 ribosomal protein". Biochimie. 78 (7): 568–576. PMID8955900. doi:10.1016/S0300-9084(96)80003-4.