Biology subjects

Springer, T.

Publications and source records attributed to Springer, T..

4 recordsLinked to original sources

bioRxiv2026

A chemically reactive and Raman-active non-canonical amino acid reveals photocycle complexity in a blue-light receptor

Photosensory protein function spans multiple time and length scales, demanding integrative approaches. We introduce 4-diacetylenyl-phenylalanine (DAF), a dual-purpose non-canonical amino acid (ncAA) that enables both chemical control and spectroscopic readout of photoreceptor dynamics. Genetically encoded in E. coli, DAF combines a reactive diyne for bioorthogonal ligations (thiols, azides, tetrazines) with a strong, solvatochromic Raman signal in the cell-silent region. Applied to the light-oxygen-voltage (LOV) transcription factor EL222, DAF enables multifaceted interrogation of its photocycle. We engineer a covalently cross-linked variant that suppresses light-driven conformational changes and DNA binding, and generate a donor-acceptor construct for Forster resonance energy transfer (FRET) tracking of photoinduced structural dynamics. Time-resolved stimulated Raman spectroscopy following flavin mononucleotide (FMN) excitation reveals additional processes -from vibrational energy transfer to local unfolding-spanning femtoseconds to milliseconds. DAF thus constitutes a versatile tool to resolve protein dynamics with high spatiotemporal resolution.

biochemistry↗

bioRxiv2024

De Novo Design of Integrin α5β1 Modulating Proteins for Regenerative Medicine

Integrin 5{beta}1 is crucial for cell attachment and migration in development and tissue regeneration, and 5{beta}1 binding proteins could have considerable utility in regenerative medicine and next-generation therapeutics. We use computational protein design to create de novo 5{beta}1-specific modulating miniprotein binders, called NeoNectins, that bind to and stabilize the open state of 5{beta}1. When immobilized onto titanium surfaces and throughout 3D hydrogels, the NeoNectins outperform native fibronectin and RGD peptide in enhancing cell attachment and spreading, and NeoNectin-grafted titanium implants outperformed fibronectin and RGD-grafted implants in animal models in promoting tissue integration and bone growth. NeoNectins should be broadly applicable for tissue engineering and biomedicine. One-Sentence SummaryA de novo-designed fibronectin substitute, NeoNectin, is specific for integrin 5{beta}1 and can be incorporated into biomaterials for regenerative medicine.

bioengineering↗

bioRxiv2020

Complement receptor 3 forms a compact high affinity complex with iC3b

Complement receptor 3 (CR3, also known as Mac-1, integrin M{beta}2, or CD11b/CD18) is expressed on a subset of myeloid and certain activated lymphoid cells. CR3 is essential for the phagocytosis of complement-opsonized particles such as pathogens and apoptotic or necrotic cells opsonized with the complement fragment iC3b and to a lesser extent C3dg. While the interaction between the iC3b thioester domain and the ligand binding CR3 M I-domain is structurally and functionally well characterized, the nature of additional CR3-iC3b interactions required for phagocytosis of complement opsonized objects remain obscure. Here we analyzed the interaction between iC3b and the 150 kDa headpiece fragment of the CR3 ectodomain. Surface plasmon resonance experiments demonstrated a 30 nM affinity of CR3 for iC3b compared to 515 nM for the iC3b thioester domain. Small angle x-ray scattering analysis revealed that iC3b adopts an extended but preferred conformation in solution. Upon interaction with CR3, iC3b rearranges to form a compact receptor-ligand complex. Overall, the data suggest that the iC3b-CR3 interaction is of high affinity and relies on minor contacts formed between CR3 and regions outside the iC3b thioester domain. Our results rationalize the more efficient phagocytosis elicited by iC3b than by C3dg and pave the way for development of specific therapeutics for treatment of inflammatory and neurodegenerative diseases that do not interfere with recognition of non-complement CR3 ligands.

biochemistry↗

bioRxiv2018

Fusion surface structure, function, and dynamics of gamete fusogen HAP2

HAP2 is a class II gamete fusogen in many eukaryotic kingdoms. A crystal structure of Chlamydomonas HAP2 shows a trimeric fusion state. Domains D1, D2.1 and D2.2 line the 3-fold axis; D3 and a stem pack against the outer surface. Surprisingly, hydrogen-deuterium exchange shows that surfaces of D1, D2.2 and D3 closest to the 3-fold axis are more dynamic than exposed surfaces. Three fusion helices in the fusion loop of each monomer expose hydrophobic residues at the trimer apex that are splayed from the 3-fold axis, leaving a solvent-filled cavity between the fusion loops in each monomer. At the base of the long fusion loop, Arg185 docks in a carbonyl cage. Comparisons to other structures, dynamics, and the greater effect on Chlamydomonas gamete fusion of mutation of axis-proximal than axis-distal fusion helices suggest that the apical portion of each monomer could tilt toward the 3-fold axis with merger of the fusion helices into a common fusion surface.

biochemistry↗