C-terminal (CT) domain of the contact-dependent growth inhibition (CDI) system (CdiA-CT) of Escherichia coli and Klebsiella pneumoniae CdiA, and similar proteins
CDI toxins are expressed by gram-negative bacteria as part of a mechanism to inhibit the growth of neighboring cells. This model represents the C-terminal (CT) toxin domain of CdiA effector proteins. CdiA secretion is dependent on the outer membrane protein CdiB. Upon binding to a receptor on the surface of target bacteria, the CDI toxin is delivered via the C-terminal. A wide variety of C-terminal toxin domains appear to exist; this particular model contains the C-terminal domain of CdiA (CdiA-CT) from Escherichia coli, Klebsiella pneumoniae and other bacteria. The exact biochemical function of this CdiA-CT is as yet unknown. CDI(+) bacteria also produce a CDI immunity protein (CdiI) to specifically neutralize the CdiA-CT toxins to prevent auto-inhibition. This CdiA-CT binds its cognate CdiI with high affinity.