Figure 2
Characterization of the Mediterranean mussel NACR (MgNACR) enzyme catalytic and structural domains. Comparison of the NACR sequence homologues from the hard-shelled mussel (McNACR) and oyster homologues with the human (HsCAII) and chicken (GgCAII) α-CAs involved in osteoclast activity and egg shell biomineralization, respectively. The pacific oyster sequences are involved in shell formation41. The seven consensus metazoan domains of α-CAs involved in biomineralization28 are indicated. The domains that contain the three histidine (H) residues (highlighted in green and bold italics) that interact with the Zn2+ ion within the catalytic site are annotated in green and the domains involved in α-CA conformation are indicated in grey. The gate-keeping residues Glutamate (E) within domain 3 and the first Threonine (T) in domain 6 that orientate the substrate for catalysis are highlighted in grey and bold. The signal peptide (SP) sequence is represented and was predicted using the SignalP 4.1 Server. The predicted size (aa- amino acids) of the deduced proteins is indicated. The residues predicted to delimit the human α-CAs active site cavity are indicated by “*”71. The pacific oyster CgCA5 was not included as it is incomplete (lacks domains II and III).
