TY  - JOUR
A1  - Broeker, Nina K.
A1  - Kiele, Franziska
A1  - Casjens, Sherwood R.
A1  - Gilcrease, Eddie B.
A1  - Thalhammer, Anja
A1  - Koetz, Joachim
T1  - In Vitro Studies of Lipopolysaccharide-Mediated DNA Release of Podovirus HK620
JF  - Viruses
N2  - Gram-negative bacteria protect themselves with an outermost layer containing lipopolysaccharide (LPS). O-antigen-specific bacteriophages use tailspike proteins (TSP) to recognize and cleave the O-polysaccharide part of LPS. However, O-antigen composition and structure can be highly variable depending on the environmental conditions. It is important to understand how these changes may influence the early steps of the bacteriophage infection cycle because they can be linked to changes in host range or the occurrence of phage resistance. In this work, we have analyzed how LPS preparations in vitro trigger particle opening and DNA ejection from the E. coli podovirus HK620. Fluorescence-based monitoring of DNA release showed that HK620 phage particles in vitro ejected their genome at velocities comparable to those found for other podoviruses. Moreover, we found that HK620 irreversibly adsorbed to the LPS receptor via its TSP at restrictive low temperatures, without opening the particle but could eject its DNA at permissive temperatures. DNA ejection was solely stimulated by LPS, however, the composition of the O-antigen dictated whether the LPS receptor could start the DNA release from E. coli phage HK620 in vitro. This finding can be significant when optimizing bacteriophage mixtures for therapy, where in natural environments O-antigen structures may rapidly change.
KW  - O-antigen specific phage
KW  - podovirus
KW  - HK620
KW  - lipopolysaccharide
KW  - in vitro particle opening
KW  - tailspike protein
Y1  - 2018
U6  - https://doi.org/10.3390/v10060289
SN  - 1999-4915
VL  - 10
IS  - 6
SP  - 1
EP  - 15
PB  - Molecular Diversity Preservation International (MDPI)
CY  - Basel
ER  - 
TY  - JOUR
A1  - Navarro-Retamal, Carlos
A1  - Bremer, Anne
A1  - Ingolfsson, Helgi I.
A1  - Alzate-Morales, Jans
A1  - Caballero, Julio
A1  - Thalhammer, Anja
A1  - Gonzalez, Wendy
A1  - Hincha, Dirk K.
T1  - Folding and Lipid Composition Determine Membrane Interaction of the Disordered Protein COR15A
JF  - Biophysical journal
N2  - Plants from temperate climates, such as the model plant Arabidopsis thaliana, are challenged with seasonal low temperatures that lead to increased freezing tolerance in fall in a process termed cold acclimation. Among other adaptations, this involves the accumulation of cold-regulated (COR) proteins, such as the intrinsically disordered chloroplast-localized protein COR15A. Together with its close homolog COR15B, it stabilizes chloroplast membranes during freezing. COR15A folds into amphipathic alpha-helices in the presence of high concentrations of low-molecular-mass crowders or upon dehydration. Under these conditions, the (partially) folded protein binds peripherally to membranes. In our study, we have used coarse-grained molecular dynamics simulations to elucidate the details of COR15A-membrane binding and its effects on membrane structure and dynamics. Simulation results indicate that at least partial folding of COR15A and the presence of highly unsaturated galactolipids in the membranes are necessary for efficient membrane binding. The bound protein is stabilized on the membrane by interactions of charged and polar amino acids with galactolipid headgroups and by interactions of hydrophobic amino acids with the upper part of the fatty acyl chains. Experimentally, the presence of liposomes made from a mixture of lipids mimicking chloroplast membranes induces additional folding in COR15A under conditions of partial dehydration, in agreement with the simulation results.
Y1  - 2018
U6  - https://doi.org/10.1016/j.bpj.2018.08.014
SN  - 0006-3495
SN  - 1542-0086
VL  - 115
IS  - 6
SP  - 968
EP  - 980
PB  - Cell Press
CY  - Cambridge
ER  -