In eubacteria, the tmRNA system frees ribosomes that stall during protein synthesis and adds an ssrA tag to the incompletely translated polypeptide to target it for degradation. The AAA+ ClpXP protease degrades most ssrA-tagged proteins in the Escherichia coli cytoplasm and was recently shown to degrade an ssrA-tagged protein in the inner membrane. However, we find that tmRNA-mediated tagging of E. coli ProW1-182, a different inner-membrane protein, results in degradation by the membrane-tethered AAA+ FtsH protease. ClpXP played no role in the degradation of ProW1-182 in vivo. These studies suggest that a complex distribution of proteolytic labor maintains protein quality control in the inner membrane.