Journal of Proteomics & Bioinformatics
Open Access
ISSN: 0974-276X
+44 1223 790975
ISSN: 0974-276X
+44 1223 790975
John B Bruning
The University of Adelaide, Australia
Scientific Tracks Abstracts: J Proteomics Bioinform
The human sliding clamp (also known as PCNA) controls access to DNA of many of the proteins involved in essential processes such as DNA replication, DNA repair and cell cycle control. Proteins compete for interaction with the PCNA surface by means of a short, conserved peptide sequence known as the PCNA-interacting protein motif (or PIP-box). Binding to PCNA via the PIP box allows access to DNA. For example, the major replicative polymerase, pol delta, requires PCNA for processive DNA synthesis, without interaction with PCNA the polymerase dissociates from DNA and is incapable of processive DNA synthesis. As such, many groups have proposed the usefulness of PIP box mimetics for use as cancer therapeutics given they would block upregulated PCNA form allowing interaction with pol delta and hence would inhibit DNA replication. However, no peptide mimetics of PCNA have been forthcoming to date. Here we describe the design and synthesis of the first PCNA peptidomimetic. Our mimetic, ACR2, was designed through synthetic lactam chemistry to constrain the secondary structure of the peptide for optimized binding to PCNA. NMR solution studies show that the wild type p21 peptide from which ACR2 was designed adopts no defined secondary structure in solution, while our mimetic adopts a 310 helix in solution, which has been shown in previous studies to be essential for PIP box binding to PCNA. Binding experiments determined a KD of 200 nM of ACR2 for PCNA, which is higher than the wild type peptide. A co-crystal structure of ACR2 bound to hPCNA revealed the mechanism of interaction of this mimetic with PCNA. Recent Publications 1. Marshall A C, Kroker A J, Murray L A, Gronthos K, Rajapaksha H, Wegener K L and Bruning J B (2017) Structure of the sliding clamp from the fungal pathogen Aspergillus fumigatus (AfumPCNA) and interactions with Human p21. FEBS Journal 284(6):985-1002. 2. Kroker A J and Bruning J B (2015) p21 exploits residue Tyr151 as a tether for high affinity PCNA binding. Biochemistry 54(22):3483-93. 3. Bruning J B and Shamoo Y (2004) Structural and thermodynamic analysis of human PCNA with peptides derived from DNA polymerase-delta p66 subunit and flap endonuclease-1. Structure 12(12):2209-19. 4. Zhang X, Bruning J B, George J H and Abell A D (2016) A mechanistic study on the inhibition of α-chymotrypsin by a macrocyclic peptidomimetic aldehyde. Organic & Biomolecular Chemistry 14(29):6970-8. 5. Chua K C, Pietsch M, Zhang X, Hautmann S, Chan H Y, Bruning J B, Gütschow M and Abell A D Angew (2014) Macrocyclic protease inhibitors with reduced peptide character. Angewandte Chemie 53(30):7828-31.