ErbB2 signaling pathways are linked to breast cancer formation, growth, and aggression; therefore, understanding the behavior of proteins associated with these pathways as well as regulatory factors that influence ErbB2 function is essential. MEMO1 is a redox active protein that is shown to associate with phosphorylated ErbB2 and mediate cell motility. We have developed a fluorescence polarization assay to probe the interaction between MEMO1 and an ErbB2-derived peptide containing a phosphorylated tyrosine residue. This interaction is shown to be pH-dependent and stronger with longer peptides as would be expected for protein-protein interactions. We have quantitatively mapped the binding interface of MEMO1 to the peptide using the fluorescence polarization assay and molecular dynamics simulations. We have confirmed that phosphorylation of the peptide is essential for binding and through mutagenesis have identified residues that contribute to favorable interactions. Our results highlight the importance of the protein-protein interactions of MEMO1 that complement the oxidase activity. In the future, these studies will provide a method for screening for selective modulators of MEMO1, which will allow for additional biological investigations.

Recent experiments indicate that the C-Jun aminoterminal kinase-interacting protein 1 (JIP1) binds to and activates the c-Jun N-terminal kinase (JNK) protein. JNK is an integral part of cell apoptosis, and misregulation of this process is a causative factor in diseases such as Alzheimer's disease (AD), obesity, and cancer. It has also been shown that JIP1 may increase the phosphorylation of tau by facilitating the interaction between the tau protein and JNK, which could also be a causative factor in AD. Very little is known about the structure and dynamics of JIP1; however, the amino acid composition of the first 350 residues suggests that it contains an intrinsically disordered region. Molecular dynamics (MD) simulations using AMBER 14 were used to study the structure and dynamics of a functionally active JIP1 10mer fragment to better understand the solution behavior of the fragment. Two microseconds of unbiased MD was performed on the JIP1 10mer fragment in 10 different seeds for a total of 20 μs of simulation time, and from this, seven structurally stable conformations of the 10mer fragment were identified via classical clustering. The 10mer ensemble was also used to build a Markov state model (MSM) that identified four metastable states that encompassed six of the seven conformational families identified by classical dimensional reduction. Based on this MSM, conformational interconversions between the four states occur via two dominant pathways with probability fluxes of 55 and 44% for each individual pathway. Transitions between the initial and final states occur with mean first passage times of 31 (forward) and 16 (reverse) μs.

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SARS-CoV-2 is a coronavirus that has created a global pandemic. The virus contains a spike protein which has been shown to bind to the ACE2 receptor on the surface of human cells. Vaccines have been developed that recognize elements of the SARS-CoV-2 spike protein and they have been successful in preventing infection. Recently, the omicron variant of the SARS-CoV-2 virus was reported and quickly became a variant of concern due to its transmissibility. This variant contained an unusually large number (32) of point mutations, of which 15 of those mutations are in the receptor binding domain of the spike protein. In order to assess the differential binding ability of the wild type and omicron variant of the RBD spike protein to human ACE2 receptors, we conducted 2 μs of molecular dynamics simulation to estimate the binding affinities and behaviors. Based upon MM-GBSA binding affinity, center of mass distance measurements, ensemble clustering, pairwise residue decomposition and hydrogen bonding analysis, we can conclude that the 15 point mutations in the receptor binding domain do not increase the affinity of the spike protein for the human ACE2 receptor. The MM-GBSA binding estimations over a 2 μs trajectory, suggest that the wild type binds to ACE2 with a value of -29.69 kcal/mol while the omicron mutant binds with an energy value of -26.67 kcal/mol. These values are within the error estimates of the MM-GBSA method. While some mutations increase binding, more mutations diminish binding, leading to an overall similar picture of binding.

Phosphorylation‐dependent protein–protein interactions play a significant role in biological signaling pathways; therefore, small molecules that are capable of influencing these interactions can be valuable research tools and have potential as pharmaceutical agents. MEMO1 (mediator of ErbB2‐cell driven motility) is a phosphotyrosine‐binding protein that interacts with a variety of protein partners and has been found to be upregulated in breast cancer patients. Herein, we report the first small‐molecule inhibitors of MEMO1 interactions identified through a virtual screening platform and validated in a competitive fluorescence polarization assay. Initial structure–activity relationships have been investigated for these phenazine‐core inhibitors and the binding sites have been postulated using molecular dynamics simulations. The most potent biochemical inhibitor is capable of disrupting the large protein interface with a KI of 2.7 μm. In addition, the most promising phenazine core compounds slow the migration of breast cancer cell lines in a scratch assay.