Cellular retinoic acid binding protein 2 (CRABP2) transports retinoic acid from the cytoplasm to the nucleus where it then transfers its cargo to retinoic acid receptor-containing complexes leading to activation of gene transcription. We demonstrate using purified proteins that CRABP2 is also a cyclin D3-specific binding protein and that the CRABP2 cyclin D3 binding site and the proposed CRABP2 nuclear localization sequence overlap. Both sequences are within the helix-loop-helix motif that forms a lid to the retinoic acid binding pocket. Mutations within this sequence that block both cyclin D3 and retinoic acid binding promote formation of a CRABP2 structure in which the retinoic acid binding pocket is occupied by an alternative lid conformation. Structural and functional analysis of CRABP2 and cyclin D3 mutants combined with AlphaFold models of the ternary CDK4/6-cyclin D3-CRABP2 complex supports the identification of an α-helical protein binding site on the cyclin D3 C-terminal cyclin box fold.

Pseudaminic acid is a non-mammalian sugar found in the surface glycoconjugates of many bacteria, including several human pathogens, and is a virulence factor thought to facilitate immune evasion. The final step in the biosynthesis of the nucleotide activated form of the sugar, CMP-Pse5Ac7Ac is performed by a CMP-Pse5Ac7Ac synthetase (PseF). Here we present the biochemical and structural characterization of PseF from Aeromonas caviae (AcPseF), with AcPseF displaying metal-dependent activity over a broad pH and temperature range. Upon binding to CMP-Pse5Ac7Ac, AcPseF undergoes dynamic movements akin to other CMP-ulosonic acid synthetases. The enzyme clearly discriminates Pse5Ac7Ac from other ulosonic acids, through active site interactions with side-chain functional groups and by positioning the molecule in a hydrophobic pocket. Finally, we show that AcPseF binds the CMP-Pse5Ac7Ac side chain in the lowest energy conformation, a trend that we observed in the structures of other enzymes of this class.

During drug discovery, it is crucial to exclude compounds with toxic effects. The human ether-à-go-go-related gene (hERG) channel is essential for maintaining cardiac repolarization and is a critical target in drug safety evaluation due to its role in drug-induced arrhythmias. Inhibition of the hERG channel can lead to severe cardiac issues, including Torsades de Pointes tachycardia. Understanding hERG inhibition mechanisms is essential to avoid these toxicities. Several structural studies have elucidated the interactions between inhibitors and hERG. However, orientation and resolution issues have so far limited detailed insights. Here, we used digitonin to analyze the apo state of hERG, which resolved orientation issues and improved the resolution. We determined the structure of hERG bound to astemizole, showing a clear map in the pore pathway. Using this strategy, we also analyzed the binding modes of E-4031 and pimozide. These insights into inhibitor interactions with hERG may aid safer drug design and enhance cardiac safety.

Sebagai infrastruktur pengendali banjir Bendungan Kedung Ombo dilengkapi sebuah sistem pengoperasian waduk yang disebut operasi banjir. Operasi banjir dimulai saat elevasi muka air waduk (MAW) mencapai elevasi +89,50 mdpl atau disebut elevasi dumping energy level. Pada saat terjadi banjir elevasi MAW terus meningkat hingga limpas melalui pelimpah utama (+90,00 mdpl) hingga pelimpah darurat (93,30 mdpl dan 93,70 mdpl). Pelimpah darurat Kedung Ombo merupakan pelimpah timbunan yang didesain akan runtuh apabila terjadi overtopping 30 cm diatas mercu. Meskipun diperbolehkan untuk runtuh, sebaiknya hal ini harus dihindari karena akan menyebabkan limpasan air waduk yang besar sehingga dapat membanjiri daerah hilir bendungan. Maka dari itu diperlukan upaya analisis dini untuk mengetahui berapa besaran debit inflow yang disyaratkan supaya tidak terjadi keruntuhan pada pelimpah darurat. Metode penelitian yang digunakan dengan melakukan pemodelan DAS dan waduk menggunakan software HEC-HMS. Debit yang digunakan untuk menentukan besaran inflow menggunakan debit desain berbagai kala ulang yang disimulasikan terhadap waduk dan pelimpah (spillway routing) dengan ketentuan pola operasi banjir Kedung Ombo. Hasil peneluruan banjir menunjukan MAW tidak limpas pada banjir desain Q2, sedangkan waduk limpas melalui pelimpah utama pada banjir desain Q5, Q10, Q20, Q25, Q50, Q100, Q200, Q500, Q1000, dan QPMF. Pada debit banjir QPMF terjadi limpas melalui pelimpah darurat I (+93,30 mdpl) dengan elevasi MAW maksimum +93,58 mdpl. Maka dapat simpulkan bahwa operasi banjir Kedung Ombo tidak aman terhadap debit inflow QPMF.

SummaryImmunoglobulin G (IgG) antibodies that bind their cognate antigen in a pH-dependent manner (acid-switched antibodies) can release their bound antigen for degradation in the acidic environment of endosomes, while the IgGs are rescued by the neonatal Fc receptor (FcRn). Thus, such IgGs can neutralize multiple antigens over time and therefore be used at lower doses than their non-pH-responsive counterparts. Here, we show that light-chain shuffling combined with phage display technology can be used to discover IgG1 antibodies with increased pH-dependent antigen binding properties, using the snake venom toxins, myotoxin II and α-cobratoxin, as examples. We reveal differences in how the selected IgG1s engage their antigens and human FcRn and show how these differences translate into distinct cellular handling properties related to their pH-dependent antigen binding phenotypes and Fc-engineering for improved FcRn binding. Our study showcases the complexity of engineering pH-dependent antigen binding IgG1s and demonstrates the effects on cellular antibody-antigen recycling.