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).