ClpV

ClpV is an ATPase associated with the type VI secretion system (T6SS) in many Gram-negative bacteria. It belongs to the Clp/Hsp100 family of AAA+ ATPases and typically functions as a hexameric ring that uses energy from ATP hydrolysis to remodel protein substrates rather than to proteolyze them.

The primary role of ClpV in T6SS biology is to disassemble the contracted sheath that encases the secretion tube. The T6SS sheath is composed of VipA and VipB (also known as TssB and TssC in some species). After the secretion event, the contracted sheath needs to be recycled for subsequent rounds of firing. ClpV recognizes the contracted VipA/VipB sheath and disassembles it, releasing subunits that can be reused to assemble new sheaths. This recycling mechanism is important for enabling rapid and repeated secretion.

Structure and mechanism: ClpV contains a central AAA+ ATPase domain and an N-terminal domain that mediates specific interactions with the contracted sheath. It is an ATP-dependent disassembler rather than a proteolytic enzyme, distinguishing it from other Clp family proteases that pair with proteolytic partners like ClpP.

Distribution and significance: clpV genes are commonly found within T6SS gene clusters across diverse bacteria, including Vibrio, Pseudomonas, and Rhodobacter species. While essential for efficient T6SS function in many organisms, some systems utilize alternative mechanisms for sheath recycling or can operate with reduced dependence on ClpV.

Biological impact: By facilitating rapid turnover of the T6SS sheath, ClpV contributes to interbacterial competition and, in some pathogens, virulence, influencing microbial community dynamics and host interactions.