Biology subjects

Donaldson, L.

Publications and source records attributed to Donaldson, L..

3 recordsLinked to original sources

bioRxiv2024

Structural analyses of apolipoprotein A-IV polymorphisms Q360H and T347S elucidate the inhibitory effect against thrombosis

Apolipoprotein A-IV (apoA-IV) is an abundant lipid-binding protein in blood plasma. We previously reported that apoA-IV, as an endogenous inhibitor, competitively binds platelet IIb{beta}3 integrin from its N-terminal residues, reducing the potential risk of thrombosis. This study aims to investigate how the apoA-IVQ360H and apoA-IVT347S mutations affect the structure and function of apoA-IV. These mutations are linked to increased risk of cardiovascular diseases due to multiple single-nucleotide polymorphisms in the C-terminal region of apoA-IV. We postulate the structural hindrance caused by the C-terminal motifs may impede the binding of apoA-IV to platelets at its N-terminal binding site. However, the mechanistic impact of Q360H and T347S polymorphisms on this intermolecular interaction and their potential contribution to the development of cardiovascular disease have not been adequately investigated. To address this, recombinant forms of human apoA-IVWT, apoA-IVQ360H, apoA-IVT347S variants were produced, and the structural stability, dimerization, and molecular dynamics of the C-terminus were examined utilizing biophysical techniques including fluorescence anisotropy, fluorescence spectrophotometry, circular dichroism, and biolayer interferometry methods. Our results showed a deceased fraction of -helix structure in apoA-IVQ360H and apoA-IVT347S compared to the wildtype, and the inhibitory effect of dimerized apoA-IV on platelet aggregation was reduced in apoA- IVQ360H and apoA-IVT347S variants. Binding kinetics of examined apoA-IV polymorphisms to platelet IIb{beta}3 suggest a potential mechanism for increased risk of cardiovascular diseases in individuals with apoA-IVQ360H and apoA-IVT347S polymorphisms.

biochemistry↗

bioRxiv2023

NMR structure of the carboxy-terminal domain of the Ea22 pro-lysogenic protein from lambda bacteriophage

The ea22 gene resides in a relatively uncharacterized region of the lambda bacteriophage genome between the exo and xis genes and is among the earliest genes transcribed upon infection. In lambda and Shiga toxin-producing phages found in enterohemorrhagic E. coli (EHEC) associated with food poisoning, Ea22 favors a lysogenic over lytic developmental state. The Ea22 protein may be considered in terms of three domains: a short amino-terminal domain, a coiled-coiled domain, and a carboxy-terminal domain (CTD). While the full-length protein is tetrameric, the CTD is dimeric when expressed individually. Here, we report the NMR solution structure of the Ea22 CTD that is described by a mixed alpha-beta fold with a dimer interface reinforced by salt bridges. A conserved mobile loop may serve as a ligand for an unknown host protein that works with Ea22 to promote bacterial survival and the formation of new lysogens. From sequence and structural comparisons, the CTD distinguishes lambda Ea22 from homologs encoded by Shiga toxin-producing bacteriophages.

molecular biology↗

bioRxiv2019

The Arabidopsis Diacylglycerol Kinase 4 is involved in nitric oxide-dependent pollen tube guidance and fertilization

Nitric oxide (NO) is a key signaling molecule that regulates diverse biological processes in both animals and plants. In animals, NO regulates vascular wall tone, neurotransmission and immune response while in plants, NO is essential for development and responses to biotic and abiotic stresses [1-3]. Interestingly, NO is involved in the sexual reproduction of both animals and plants mediating physiological events related to the male gamete [2, 4]. In animals, NO stimulates sperm motility [4] and binding to the plasma membrane of oocytes [5] while in plants, NO mediates pollen-stigma interactions and pollen tube guidance [6, 7]. NO generation in pollen tubes (PTs) has been demonstrated [8] and intracellular responses to NO include cytosolic Ca2+ elevation, actin organization, vesicle trafficking and cell wall deposition [7, 9]. However, the NO-responsive proteins that mediate these responses are still elusive. Here we show that PTs of Arabidopsis lacking the pollen-specific Diacylglycerol Kinase 4 (DGK4) grow slower and become insensitive to NO-dependent growth inhibition and re-orientation responses. Recombinant DGK4 protein yields NO-responsive spectral and catalytic changes in vitro which are compatible with a role in NO perception and signaling in PTs. NO is a fast, diffusible gas and, based on our results, we hypothesize it could serve in long range signaling and/or rapid cell-cell communication functions mediated by DGK4 downstream signaling during the progamic phase of angiosperm reproduction.

plant biology↗