PHDs are small, independently folded, 50-80 residue long protein domains. Over 170 sequences have been annotated as PHD fingers in the human genome. They contain conserved regions of cysteine and histidine residues that coordinate two Zn 2+ ions in a cross braced fashion, with an antiparallel two-stranded β-sheet core, which imposes conformational stability. These domains read a range of histone marks, notably the methylation state of the K4 residue of H3 histone (H3K4Me 3, H3K4Me 2 or H3K4Me 0 ), and the H3K9 and H3R2 positions. Mutations within this motif have been linked to immunological, neurological and developmental disorders. TRIM33 and TRIM66. The PHD (lilac) and BRD (purple) domains of TRIM proteins sit at the Nterminus of the proteins. The TRIM family C-VI proteins (TRIM24, TRIM28 and TRIM33) and the homologous TRIM66 possess a tandem PHD-BRD cassette. TRIM24, TRIM33, and TRIM66 are in BRD Family V. D. The TRIM24 PHD-BRD has 62.0% identity and 75.5% similarity with TRIM33α. The TRIM24 PHD-BRD has 67.8% identity and 82.5% similarity with TRIM33β.