APOBEC ("apolipoprotein B mRNA editing enzyme, catalytic polypeptide-like") is a family of evolutionarily conserved cytidine deaminases.
A mechanism of generating protein diversity is mRNA editing. Members of this family are C-to-U editing enzymes. The N-terminal domain of APOBEC like proteins is the catalytic domain, while the C-terminal domain is a pseudocatalytic domain. More specifically, the catalytic domain is a zinc dependent cytidine deaminase domain and is essential for cytidine deamination. RNA editing by APOBEC-1 requires homodimerisation and this complex interacts with RNA binding proteins to form the editosome.
In humans/mammals they help protect from viral infections. These enzymes, when misregulated, are a major source of mutation in numerous cancer types.
A 2013 review discussed the structural and biophysical aspects of APOBEC3 family enzymes. Much of the APOBEC protein features are described in the widely studied APOBEC3G's page.
^PDB: 2NYT; Prochnow, C.; Bransteitter, R.; Klein, M.G.; Goodman, M.F.; Chen, X.S.; functional implications for the deaminase AID. (2007). "The APOBEC-2 crystal structure". Nature. 445 (7126): 447–451. PMID17187054. doi:10.1038/nature05492.; rendered using PyMOL.
^Wedekind JE, Dance GS, Sowden MP, Smith HC (April 2003). "Messenger RNA editing in mammals: new members of the APOBEC family seeking roles in the family business". Trends Genet. 19 (4): 207–16. PMID12683974. doi:10.1016/S0168-9525(03)00054-4.