The class V plant chitinases have a glycosyl hydrolase family 18 (GH18) domain, but lack the chitin-binding domain present in other GH18 enzymes. The GH18 domain of the class V chitinases has endochitinase activity in some cases and no catalytic activity in others. Included in this family is a lectin found in black locust (Robinia pseudoacacia) bark, which binds chitin but lacks chitinase activity. Also included is a chitinase-related receptor-like kinase (CHRK1) from tobacco (Nicotiana tabacum), with an N-terminal GH18 domain and a C-terminal kinase domain, which is thought to be part of a plant signaling pathway. The GH18 domain of CHRK1 is expressed extracellularly where it binds chitin but lacks chitinase activity.