Homo and hetero dimerisation of the human guanylate‐binding proteins hGBP‐1 and hGBP‐5 characterised by affinities and kinetics. (17th April 2018) - Kutsch, Miriam
Abstract : The human guanylate‐binding proteins (hGBPs) exhibit diverse antipathogenic and tumour‐related functions which make them key players in the innate immune response. The isoforms hGBP‐1 to hGBP‐5 form homomeric complexes and localise to specific cellular compartments. Upon heteromeric interactions, hGBPs are able to guide each other to their specific compartments. Thus, homo‐ and heteromeric interactions allow the hGBPs to build a network within the cell which might be important for their diverse biological functions. We characterised homomeric complexes of hGBPs in vitro and presented most recently that nonprenylated hGBP‐1 and hGBP‐5 form dimers as highest oligomeric species while farnesylated hGBP‐1 is able to form polymers. We continued to work on the biochemical characterisation of the heteromeric interactions between hGBPs and present here results for nonprenylated hGBP‐1 and hGBP‐5. Multiangle light scattering identified the GTP‐dependent heteromeric complex as dimer. Also hGBP‐5's tumour‐associated splice variant (hGBP‐5ta) was able to form a hetero dimer with hGBP‐1. Intriguingly, both hGBP‐5 splice variants were able to induce domain rearrangements within hGBP‐1. We further characterised the homo and hetero dimers with Förster resonance energy transfer‐based experiments. This allowed us to obtain affinities and kinetics of the homo and hetero dimer formation. Furthermore, we identified that the LG domains of hGBP‐1 and hGBP‐5 build an interaction site within the hetero dimer. Our in vitro study provides mechanistic insights into the homomeric and heteromeric interactions of hGBP‐1 and hGBP‐5 and present useful strategies to characterise the hGBP network further. Abstract : Within the family of human guanylate‐binding proteins (hGBPs) members are able to form homomeric and heteromeric complexes. Here, we present affinities and kinetics for the homo and hetero dimerisation of hGBP‐1 and hGBP‐5 and thus start to characterise the hGBP network biochemically. We identified that mechanistic details important for the proteins' homo dimerisation are also crucial for their hetero dimerisation.