Gordon Lloyd undertook his undergraduate studies at Monash University, graduating with a Bachelor of Science Degree (majoring in Biochemistry and Genetics). Upon completing his BSc, Gordon completed an honours year (First Class) in the Whisstock laboratory (Department of Biochemistry and Molecular Biology), investigating the prokaryotic serine protease inhibitor Tengpin from a functional and structural perspective (under the co-supervision of Dr Ruby Law and Ms Qingwei Zhang).
Since completing his honours year in 2007, Gordon has been working as a Research Assistant in the Whisstock Laboratory. Gordon's major research focus is investigating the structure and function of the MACPF/CDC super family of pore forming toxins. Examples of this superfamily include bacterial virulence factors (e.g. Cholesterol Dependent Cytolysins, CDCs) and proteins of the immune system (called the Membrane Attack Complex proteins and perforin, MACPF). The MACPF/CDCs are synthesised as monomeric soluble proteins and, upon binding to their target membrane, these monomers firstly oligomerize, and then change conformation. This conformational change results in two α-helical regions (TMH1 and TMH2) unwinding to form four amphipatic β-strands, which then insert through the target cell membrane, thereby forming a pore.
Recently Dr Ruby Law from our laboratory solved the structure of the mouse perforin monomer (Law et al., 2010. Nature 468: 447-451). This paper revealed the molecular mechanism of perforin’s pore formation by X-ray crystal data coupled with cryo-electron microscopy reconstruction of the perforin pore. However, what still remains unknown is the interactions perforin uses to bind to its target membrane. Studies on perforin have revealed the C2 domain (a calcium dependent phospholipid binding domain) is responsible for the initial interaction with the cell membrane. Therefore to investigate these cellular interactions, under the supervision of Dr Ruby Law and Dr Daouda Traore, our laboratory has isolated the C2 domain of mouse perforin. We have also cloned, expressed and purified the perforin-like C2 domains of Scopthtamus maximus and Sparus aurata. The intact C2 domains of these two species of fish are active proteins involved in immune response and can therefore be considered as good models for studying the structural basis of calcium and membrane binding of the perforin C2 domains. We recently solved the crystal structures of these proteins, revealing they match the conserved architecture of the C2 domain (consisting of eight anti parallel β-strands connected by flexible loops, to form a β-sandwich). We also identified in our structures, the fully occupied calcium binding sites. Not only are these calcium binding sites important in stabilising flexible loops in the structure, they are possibly involved in interactions with the negative head group of membrane phospholipids. Although some progress has been made, still very little is known about the molecular mechanism of C2 domain binding to cellular membranes. Our laboratory is trying to address this question, by the co-crystallization of C2 domains with a wide variety of lipids.