Biomolecular Science and Engineering Program, University of California, Santa Barbara, CA, USA; Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, CA, USA. Electronic address:
Published: November 2019
AI Article Synopsis
Article Abstract
Contact-dependent growth inhibition (CDI) is a form of interbacterial competition mediated by CdiB-CdiA two-partner secretion systems. CdiA effector proteins carry polymorphic C-terminal toxin domains (CdiA-CT), which are neutralized by specific CdiI immunity proteins to prevent self-inhibition. Here, we present the crystal structures of CdiA-CT⋅CdiI complexes from Klebsiella pneumoniae 342 and Escherichia coli 3006. The toxins adopt related folds that resemble the ribonuclease domain of colicin D, and both are isoacceptor-specific tRNases that cleave the acceptor stem of deacylated tRNA. Although the toxins are similar in structure and substrate specificity, CdiA-CT activity requires translation factors EF-Tu and EF-Ts, whereas CdiA-CT is intrinsically active. Furthermore, the corresponding immunity proteins are unrelated in sequence and structure. CdiI forms a dimeric β sandwich, whereas CdiI is an α-solenoid monomer. Given that toxin-immunity genes co-evolve as linked pairs, these observations suggest that the similarities in toxin structure and activity reflect functional convergence.
Background: Species host diverse microbial communities that can impact their digestion and health, which has led to much interest in understanding the factors that influence their microbiota. We studied the developmental, environmental, and social factors that influence the microbiota of nestling barn owls (Tyto alba) through a partial cross-fostering experiment that manipulated the social and nest environment of the nestlings. We then examined the nestling microbiota before and three weeks after the exchange of nestlings between nests, along with the microbiota of the adults at the nest and nestlings in unmanipulated nests.
The electrochemical nitrate reduction reaction (NORR) involves multiple hydrogenation and deoxygenation steps, which compete with the hydrogen evolution reaction (HER). Therefore, NORR driven in acidic media is challenging in spite of advantageous fast hydrogen transfers in its elementary steps. The findings presented in this article first demonstrate that the NORR is significantly activated even in acidic lithium nitrate solutions at LiNO concentrations exceeding 6 m on a Pt electrode (the highly effective catalyst for HER) by the formation of a "hydronium-in-salt" electrolyte (HISE), a new type of aqueous high concentration salt electrolyte.
Inarguably, the green fluorescent protein (GFP) family is an exemplary model for protein engineering, accessing a range of unparalleled functions and utility in biology. The first variant to recognize and provide an optical output of chloride in living cells was serendipitously uncovered more than 25 years ago. Since then, researchers have actively expanded the potential of GFP indicators for chloride through site-directed and combinatorial site-saturation mutagenesis, along with chimeragenesis.
Shared polymorphisms, loci with identical alleles across species, are of unique interest in evolutionary biology as they may represent cases of selection maintaining ancient genetic variation post-speciation, or contemporary selection promoting convergent evolution. In this study, we investigate the abundance of shared polymorphism between two members of the Daphnia pulex species complex. We test whether the presence of shared mutations is consistent with the action of balancing selection or alternative hypotheses such as hybridization, incomplete lineage sorting or convergent evolution.
The potential of cannabinoids to address public health challenges has stimulated exploration into alternative sources and production technologies. Radula marginata, an endemic Aotearoa/New Zealand liverwort, produces the bibenzyl cannabinoid perrottetinene (PET), analogous to Cannabis psychoactive tetrahydrocannabinol (THC). Structural differences between PET and THC could alter therapeutic interactions and mitigate adverse side effects.
