This is the N-terminal zinc-binding domain of 23S rRNA (guanine(745)-N(1))-methyltransferase RlmA from E. coli and similar proteins, which is responsible for specific recognition and binding of its rRNA substrate [1].

1: Crystal structure of RlmAI: implications for understanding the 23S rRNA G745/G748-methylation at the macrolide antibiotic-binding site. Das K, Acton T, Chiang Y, Shih L, Arnold E, Montelione GT; Proc Natl Acad Sci U S A. 2004;101:4041-4046. PMID:14999102