1.B.1.7.2
Sugar-specific chitoporin of 375 aas, ChiP.  The best substrate is chitohexose, but ChiP  transports a variety of chitooligosaccharides.  Trp136 is important for the binding affinity for chitohexaose (Chumjan et al. 2015). X-ray crystal structures of ChiP from V. harveyi in the presence and absence of chito-oligosaccharides have been solved (Aunkham et al. 2018). Structures without bound sugar reveal a trimeric assembly with an unprecedented closing of the transport pore by the N-terminus of a neighboring subunit. Substrate binding ejects the pore plug to open the transport channel.The structures explain the exceptional affinity of ChiP for chito-oligosaccharides and point to an important role of the N-terminal gate in substrate transport (Aunkham et al. 2018). Hydrogen-bonds contribute to sugar permeation (Chumjan et al. 2019). This protein is 90% identical to the chitoporin of the Vibrio campbellii chitoporin (Aunkham et al. 2020). The C2 entity of chitosugars is crucial for the molecular selectivity of the Vibrio campbellii chitoporin (Suginta et al. 2021).