Iron-regulated envelope proteins of mycobacteria grown in vitro and their occurrence inMycobacterium avium andMycobacterium leprae grown in vivo

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Abstract
Several iron-regulated envelope proteins (IREPs), 11–180 kDa, have been detected in preparations of walls and membranes ofMycobacterium smegmatis, in an armadillo-derived mycobacterium (ADM) and inM. avium. The same sized proteins fromM. vaccae appeared under both iron-deficient and iron-sufficient growth conditions. Two larger proteins, of 240 and 250 kDa, appeared in the membranes ofM. smegmatis andM. avium only when grown iron-sufficiently but were constitutively present in both ADM andM. vaccae. The IREPs fromM. smegmatis were not induced under zinc-deficient growth conditions. Three of the four IREPs (14, 21 and 29 kDa) recognized inM. avium grown in vitro were also recovered from membrane fractions of the same strain grown in mice. In addition, these membranes contained both the high-molecular-mass proteins associated with iron-sufficient growth conditions. Membranes ofM. leprae, recovered from infected armadillos, showed the faint presence of a possible IREP at 29 kDa and wall preparations showed the presence of a 21-kDa protein. Membranes also contained the two larger proteins at 240 and 250 kDa. An explanation for the simultaneous occurrence of both low-iron-regulated and high-iron-regulated proteins is offered.