A constitutively expressed secondary porin, forms a water-filled channel which favors the permeation of cations and less efficiently phosphate. There are about 2400 porins in wild-type, 800 in an mspA deletion and 150 in a double mspA-mspC deletion. Octamers. Probably forms a goblet with the wide end on the exterior of the outer membrane and a central channel. It is not known if mixed oligomers of MspC with other Msp subunits form in vivo (By similarity). Constitutely expressed. Single deletion is viable, and shows no effects on glucose uptake. A double mspA-mspC deletion takes up less of the antibiotic cephaloridine, glucose, serine and phosphate than the single mspA deletion and grows slower than wt or single mspA deletion. A triple mspA-mspC-mspD deletion grows even slower and has reduced Fe(3+) transport compared to wild-type. Belongs to the mycobacterial porin (TC 1.B.24) family. It is not clear if the data in PubMed:11309127 refer to MspB or MspC as they are nearly identical.