Search

The latex of the medicinal plant Artocarpus lakoocha (A. lakoocha) , which has been shown to have potential anti-inflammatory and wound-healing capabilities, contains a novel heme-peroxidase. This protein was subjected to activity assays, fluorescence spectroscopy, and far-UV circular dichroism to investigate its structure, dynamics, and stability. The results demonstrated the presence of three folding states: the native state (N) at neutral pH, intermediate states including molten globule (MG) at pH 2 and acid-unfolded (UA) at pH 1.5 or lower, and acid-refolded (A) at pH 0.5, along with alkaline denatured (UB) at pH 8-12 and the third denatured state (D) at GuHCl concentrations exceeding 5 M. Absorbance studies indicated the presence of loosely associated form of heme in the pH range of 1-2. The protein showed stability and structural integrity across a wide pH range (3-10), temperature (70°C), and high concentrations of GuHCl (5 M) and urea (8 M). This study is the first to report multiple 'partially folded intermediate states' of A. lakoocha peroxidase, with varying amounts of secondary structure, stability, and compactness. These results demonstrate the high stability of A. lakoocha peroxidase and its potential for biotechnological and industrial applications, making it a valuable model system for further studies on its structure-function relationship., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Sonkar, Pachauri, Kumar, Choudhary and Jagannadham.)

Membrane vesicles (MVs) serve as an essential virulence factor in several pathogenic bacteria. The release of MVs by Listeria monocytogenes is only recently recognized; still, the enigmatic role of MVs in pathogenesis is yet to be established. We report the transcriptome response of Caco-2 cells upon exposure to MVs and the L. monocytogenes that leads to observe the up-regulation of autophagy-related genes in the early phase of exposure to MVs. Transcription of inflammatory cytokines is to the peak at the fourth hour of exposure. An array of differentially expressed genes was associated with actin cytoskeleton rearrangement, autophagy, cell cycle arrest, and induction of oxidative stress. At a later time point, transcriptional programs are generated upon interaction with MVs to evade innate immune signals, by modulating the expression of anti-inflammatory genes. KEGG pathway analysis is palpably confirming that MVs appear principally responsible for the induction of immune signaling pathways. Besides, MVs induced the expression of cell cycle regulatory genes, likely responsible for the ability to prolong host cell survival, thus protecting the replicative niche for L. monocytogenes . Notably, we identified several non-coding RNAs (ncRNAs), possibly involved in the regulation of early manipulation of the host gene expression, essential for the persistence of L. monocytogenes ., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2023 The Authors. Published by Elsevier B.V.)

Outer membrane vesicles (OMVs) of Acinetobacter baumannii DS002 carry proteins which perform selective biological functions. The proteins involved in cell wall/membrane biogenesis and inorganic ion transport and metabolism occupied a significant portion of the 302 proteins associated with OMVs. Interestingly, the TonB-dependent transporters (TonRs), linked to the active transport of nutrients across the energy-deprived outer membrane, are predominant among proteins involved in inorganic ion transport and metabolism. The OMVs of DS002 contain TonRs capable of transporting iron complexed to catecholate, hydroximate, and mixed types of siderophores. Consistent with this observation, the OMVs were firmly bound to ferric-enterobactin ( 55 Fe-Ent) and successfully transported iron into A. baumannii DS002 cells grown under iron-limiting conditions. In addition to the TonRs, OMVs also carry proteins known to promote pathogenesis, immune evasion, and biofilm formation. Our findings provide conclusive evidence for the role of OMVs in the transport of nutrients such as iron and show the presence of proteins with proven roles in pathogenicity and immune response. IMPORTANCE TonB-dependent transporters (TonRs) play a crucial role in transporting nutrients such as iron, nickel, copper, and complex carbohydrates across the energy-deprived outer membrane. Due to their unique structural features, TonRs capture nutrients in an energy-independent manner and transport them across the outer membrane by harvesting energy derived from the inner membrane-localized Ton-complex. In this study, we report the presence of TonRs capable of transporting various nutrients in OMVs and demonstrate their role in capturing and transporting ferric iron complexed with enterobactin into A. baumannii DS002 cells. The OMV-associated TonRs appear to play a critical role in the survival of A. baumannii, listed as a priority pathogen, under nutrient-deprived conditions.

Exploring the molecular mechanisms behind bacterial adaptation to extreme temperatures has potential biotechnological applications. In the present study, Pseudomonas sp. Lz4W, a Gram-negative psychrophilic bacterium adapted to survive in Antarctica, was selected to decipher the molecular mechanism underlying the cold adaptation. Proteome analysis of the isolates grown at 4°C was performed to identify the proteins and pathways that are responsible for the adaptation. However, many proteins from the expressed proteome were found to be hypothetical proteins (HPs), whose function is unknown. Investigating the functional roles of these proteins may provide additional information in the biological understanding of the bacterial cold adaptation. Thus, our study aimed to assign functions to these HPs and understand their role at the molecular level. We used a structured insilico workflow combining different bioinformatics tools and databases for functional annotation. Pseudomonas sp. Lz4W genome (CP017432, version 1) contains 4493 genes and 4412 coding sequences (CDS), of which 743 CDS were annotated as HPs. Of these, from the proteome analysis, 61 HPs were found to be expressed consistently at the protein level. The amino acid sequences of these 61 HPs were submitted to our workflow and we could successfully assign a function to 18 HPs. Most of these proteins were predicted to be involved in biological mechanisms of cold adaptations such as peptidoglycan metabolism, cell wall organization, ATP hydrolysis, outer membrane fluidity, catalysis, and others. This study provided a better understanding of the functional significance of HPs in cold adaptation of Pseudomonas sp. Lz4W. Our approach emphasizes the importance of addressing the "hypothetical protein problem" for a thorough understanding of mechanisms at the cellular level, as well as, provided the assessment of integrating proteomics methods with various annotation and curation approaches to characterize hypothetical or uncharacterized protein data. The MS proteomics data generated from this study has been deposited to the ProteomeXchange through PRIDE with the dataset identifier-PXD029741., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Ijaq, Chandra, Ray and Jagannadham.)