Structural basis of interaction between dimeric cyclophilin 1 and Myb1 transcription factor in Trichomonas vaginalis

Abstract

Cyclophilin 1 (TvCyP1), a cyclophilin type peptidyl-prolyl isomerase present in the human parasite Trichomonas vaginalis, interacts with Myb1 and assists in its nuclear translocation. Myb1 regulates the expression of ap65-1 gene that encodes for a disease causing cytoadherence enzyme. Here, we determined the crystal structures of TvCyP1 and its complex with the minimum TvCyP1-binding sequence of Myb1 (Myb1104–111), where TvCyP1 formed a homodimer, unlike other single domain cyclophilins. In the complex structure, one Myb1104–111 peptide was bound to each TvCyP1 protomer, with G106-P107 and Y105 fitting well into the active site and auxiliary S2 pocket, respectively. NMR data further showed that TvCyP1 can catalyze the cis/trans isomerization of P107 in Myb1104–111. Interestingly, in the well-folded Myb1 protein (Myb135–141), the minimum binding sequence adopted a different conformation from that of unstructured Myb1104–111 peptide, that could make P107 binding to the active site of TvCyP1 difficult. However, NMR studies showed that similar to Myb1104–111 peptide, Myb135–141 also interacted with the active site of TvCyP1 and the dynamics of the Myb135–141 residues near P107 was reduced upon interaction. Together, the structure of TvCyP1 and detailed structural insights on TvCyP1-Myb1 interaction provided here could pave the way for newer drugs to treat drug-resistant strains.

N-Terminal Segment of TvCyP2 Cyclophilin from Trichomonas vaginalis Is Involved in Self-Association, Membrane Interaction, and Subcellular Localization

“…Tv CyP1 is known to form a dimer in both crystal and solution states [ 35 ]. With the SEC-MALS experiment, the molecular weight of Tv CyP2 was measured at ~20.01 kDa in a solution similar to theoretical molecular weight 20.947 kDa ( Figure 2 A), Tv CyP2 forms a monomer, which agrees well with most of the single-domain CyPs but not Tv CyP1.…”

“…SEC-MALS analysis for molecular weight and oligomer state determination was performed as described [ 35 ]. Briefly, Tv CyP2 (1 mg/mL) and Tv CyP2-∆N (1 mg/mL) were used for SEC-MALS analysis.…”

“…The X-ray structures of Tv CyP2 were determined by the molecular replacement method [ 41 ] with Tv CyP1 (PDB ID 5YBA) [ 35 ] used as a starting model with the Phaser-MR program [ 42 ]. This initial modeling was solved and improved by using COOT [ 43 ] and PHENIX [ 44 ] refinement.…”

“…Previously, we reported that T. vaginalis cyclophilin 1 ( Tv Cyp1), a cyclophilin type peptidyl-prolyl isomerase and homolog of h CyPA, plays important roles in regulating the nuclear translocation of Myb1 and Myb3 proteins and forms a homodimer in both crystal and solution states with the active site residues highly exposed [ 35 ]. As compared with Tv Cyp1, Tv CyP2, containing an extra segment at the N-terminus (N-terminal segment), as shown in Figure 1 A,B, is found primarily in the endoplasmic reticulum (ER) and regulates protein trafficking of Tv CyP1 and Myb3 toward hydrogenosomes and also Tv CyP1 toward the plasma membrane [ 36 ].…”

Endomembrane Protein Trafficking Regulated by a TvCyP2 Cyclophilin in the Protozoan Parasite, Trichomonas vaginalis

“…8), the two cyclophilins may regulate the same substrates in coordination or in competition when they coexist in the same cellular compartment, but they may also exert differential effects on specific substrates in other cellular compartments. As to the structures of the two cyclophilins, TvCyP1 is a homodimer 45 , whereas TvCyP2 is a monomer like hCyPA (Chen CP, personal communication). Being dimeric renders TvCyP1 capable of binding to either a single substrate with two Gly-Pro dipeptide motifs or to two copies of the same or distinct substrates, each with a single dipeptide motif.…”