Recent advances in quantitative proteomics show that WD40 proteins play a pivotal role in numerous cellular networks. Yet, they have been fairly unexplored and their physical associations with other proteins are ambiguous. A quantitative understanding of these interactions has wide-ranging significance. WD40 repeat protein 5 (WDR5) interacts with all members of human SET1/MLL methyltransferases, which regulate methylation of the histone 3 lysine 4 (H3K4). Here, using real-time binding measurements in a high-throughput setting, we identified the kinetic fingerprint of transient associations between WDR5 and 14-residue WDR5 interaction (Win) motif peptides of each SET1 protein (SET1Win). Our results reveal that the high-affinity WDR5-SET1Win interactions feature slow association kinetics. This finding is likely due to the requirement of SET1Win to insert into the narrow WDR5 cavity, also named the Win binding site. Furthermore, our explorations indicate fairly slow dissociation kinetics. This conclusion is in accordance with the primary role of WDR5 in maintaining the functional integrity of a large multisubunit complex, which regulates the histone methylation. Because the Win binding site is considered a key therapeutic target, the immediate outcomes of this study could form the basis for accelerated developments in medical biotechnology.
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Close ModalPKA Cβ: A forgotten catalytic subunit of cAMP-dependent protein kinase opens new windows for PKA signaling and disease pathologies.
The N- and C-terminal tails (Nt-tail/Ct-Tail) of the PKA catalytic subunit wrap around the N-lobe (white shell) and C-lobe (tan shell) of the kinase core. The sequences differences, indicated as dots, between Cα and Cβ are mapped onto the Cα structure, these cluster around the Nt-Tail and the Ct-Tail and to regions of the core that are regulated by the tails. The Cβ isoforms created by different genes and splice variants differ only in the first exon (circle), a region in Cα that is important for targeting. For more information see the review by Taylor and colleagues (pp. 2101–2119) in this issue. Image provided by Susan Taylor.
Kinetics of the multitasking high-affinity Win binding site of WDR5 in restricted and unrestricted conditions
