This family includes the HopA1 effector protein from Pseudomonas syringae. Structurally this protein has an alpha + beta fold [1]. The effector protein HopA1 was shown to affect the EDS1 complex by binding EDS1 directly and activating the immune response signaling pathway.

1: Crystal structure of the effector protein HopA1 from Pseudomonas syringae. Park Y, Shin I, Rhee S; J Struct Biol. 2015;189:276-280. PMID:25681297