Gao et al, Cell Research (2016) http://www.ncbi.nlm.nih.gov/pubmed/27444870
Cpf1 is a Cas9 analog with an unknown cleavage mechanism that uses a single 42 nt-44 nt crRNA recognizing a T-rich PAM . By studying the crystal structure of Cpf1 in complex crRNA and target DNA researchers were able to start characterizing the interaction between Cpf1 and target DNA sequences. Binding to target DNA is initially disordered in the Cpf1-crRNA complex, upon target recognition an ordered conformation is established allow the PAM interacting domain to change from an open-to-closed conformation. This mechanism is distinct from that found in Cas9.