Plays a role in the extracellular assembly of CsgA into thin aggregative fimbriae (Tafi) fibers. Assembly may also require CsgE. Tafi are thought to be assembled via an extracellular nucleation-precipitation (ENP) pathway, and possibly also via an intracellular non-CsgC-dependent pathway (By similarity). Under control of the CsgD transcription factor, part of the csgBAC/ymdA operon. Belongs to the CsgC/AgfC family.