Catalysis and Binding of Cyclophilin A with Different HIV-1 Capsid Constructs

Abstract

The prolyl isomerase cyclophilin A (CypA) is required for efficient HIV-1 replication and is incorporated into virions through a binding interaction at the Gly−Pro²²² bond located within the capsid domain of the HIV-1 Gag precursor polyprotein (Pr^gag). It has recently been shown that CypA efficiently catalyzes the cis/trans isomerization of Gly−Pro²²² within the isolated N-terminal domain of capsid (CA^N). To address the proposal that CypA interacts with Gly−Pro sequences in the C-terminal domain of a mature capsid, the interaction between CypA and the natively folded, full-length capsid protein (CA^FL) has been investigated here using nuclear magnetic resonance spectroscopy. In addition, a fragment of the Pr^gag protein encoding the full-matrix protein and the N-terminal domain of capsid (MA-CA^N) has been used to probe the catalytic interaction between CypA and an immature form of the capsid. The results discussed herein strongly suggest that Gly−Pro²²² located within the N-terminal domain of the capsid is the preferential site for CypA binding and catalysis and that catalysis of Gly−Pro²²² is unaffected by maturational processing at the N-terminus of the capsid.