InterPro: IPR012284 Fibritin/6-phosphogluconate dehydrogenase, C-terminal extension

6-phosphogluconate dehydrogenase (EC:1.1.1.44) catalyses the oxidative decarboxylation of 6-phosphogluconate to ribulose 5-phosphate with the concomitant reduction of NADP to NADPH. This reaction is a component of the hexose mono-phosphate shunt and pentose phosphate pathways (PPP), which functions to generate ribose 5-phosphate for nucleotide and nucleic acid synthesis [1, 2]. Prokaryotic and eukaryotic 6PGD are proteins of about 470 amino acids whose sequences are highly conserved [3]. The protein is a homodimer in which the monomers act independently: each contains a large, mainly alpha-helical domain and a smaller beta-alpha-beta domain, containing a mixed parallel and anti-parallel 6-stranded beta sheet [2]. NADP is bound in a cleft in the small domain, and the substrate binds in an adjacent pocket [2].

This entry represents the terminal 30-40 residues of 6-phosphogluconate dehydrogenase C-terminal domain, which is lacking in certain 6PGD enzymes. The core of the C-terminal domain is represented by IPR012283. This region bears structural resemblance to the C-terminal portion of the Bacteriophage T4 fibritin protein, which is responsible for the attachment of long tail fibres to virus particles, and forms the, "whiskers", or fibres on the neck of the virion [4].