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. 2023 Feb 20;14:1108915. doi: 10.3389/fphar.2023.1108915

FIGURE 4.

FIGURE 4

Structure of IKKγ, IKKα, IKKβ and HIF-1α. (I) Represents the structure of IKKγ or NEMO. IKKγ is a 419 amino acid dimeric fragment consisting of a series of parallel intermolecular coiled coil domains (represented as CC1 and CC2). The amino acid terminus (N-terminus) is vital for interaction with IKKα and IKKβ. Linker 1 serves for interaction with viral trans activators like HTLV-1 and Tax and V-Flip. C-terminus function for signal transmission while NOA and Zinc Finger (ZF) domains bind to polyubiquitin chains. (II,III) represents the structure of IKKα and IKKβ respectively. IKKα is a 745 amino acid fragment consisting of an activation loop from amino acid 176–180 whereas IKKβ is a 756 amino acid fragment consisting of activation loop from 177–181 on amino terminous. A ubiquitin like domain is present (from amino acid 307–384) on carboxy terminous of IKKβ but not on IKKα. The function of leucine zipper domain is to allow homo and heterodimerization of the kinases. The function of helix loop helix is less clear but it seems to be involved in the modulation of kinase activity. A 40 amino acid region at the extreme carboxy terminous of the kinases (AA-705–743) is required for their interaction with NEMO. (IV)- represents the structure of HIF-1α. HIF-1α is a 826 amino acid sequence consisting of basic helix loop helix motif and a PAS domain. The sequence possess a N-terminal trans activation domain (N-TAD) on Oxygen dependent degradation domain (ODDD) of HIF-1α along with C-terminal transactivation. The HIF-1α consists of prolyl hydroxylation site at Pro402 and P4 as w ro56ell as pVHL binding site at Leu532 respectively on that lie on ODDD. The CTAD of HIF-1α consists of Asparginyl hydroxylation site at N803.