This is the C-terminal domain of 54S ribosomal protein L2 (also known as Mitochondrial large ribosomal subunit protein bL27m). bL27 C-terminal region interacts with an expansion segment of 21S rRNA to form part of the central protuberance [1].

1: Structure of the yeast mitochondrial large ribosomal subunit. Amunts A, Brown A, Bai XC, Llacer JL, Hussain T, Emsley P, Long F, Murshudov G, Scheres SHW, Ramakrishnan V; Science. 2014;343:1485-1489. PMID:24675956