It is currently believed that protein folding pathways or the proteostasis machinery of the archaeal organisms closely resembles that found in eukaryotes, rather than other prokaryotes like bacteria, at least in terms of constituent members of this system (Laksanalamai et al. However, there is no studies available vis-à-vis the organization of the chaperone machinery in archaeal organisms. The chaperone interaction networks for Plasmodium falciparum and its interconnection with human proteins predicted the involvement of chaperones in various cellular functions (Pavithra et al. ( 2009) had performed the systematic analysis of chaperones found in Saccharomyces cerevisiae and elucidated the hot spot as well as the presence of multicomponent modules in this organism. Chaperones often act as integrators and perform a regulatory role while overlapping in other network modules (Csermely et al. These chaperones interact with other proteins and act as mastermind of the cells to make efficient protein folding machinery. Chaperone proteins do not operate independently but often act as parts of complex functional networks of interacting molecules (Kampinga and Craig 2010). ![]() Molecular chaperones appear to be central components of living cells because of their interactions with a large number of proteins, while they facilitate the acquisition of the native state structure of these target proteins. Detailed analysis of such networks can additionally provide insights on robustness and efficiency of the system (Barabasi and Oltvai 2004 Sharma et al. The topological analysis of networks based on centrality statistics using measures such as degree distribution, betweenness centrality, and bottleneck score can reveal hub and essential proteins as well as modular organization of the system (Przulj et al. Protein-protein interaction networks mostly use data derived from experimental evidences like co-expression, gene neighborhood, gene fusion, co-occurrence, and text mining, present in various databases (Marcotte et al. Networks can also help in identification of key and essential nodes that are driving specific biological processes or even specific characteristics in organisms such as adaptability of extremophiles. Protein-protein interaction networks can not only help in understanding the role of individual proteins in a pathway but also often bring to fore some novel hypotheses about the cellular processes under investigation, which can be further tested in laboratories (Zak et al. Knowledge of interactions between various constituent cellular molecules is a fundamental requirement for better understanding of pathways at system level (Raman 2010). Comprehensive comparison of these networks leads to several interesting conclusions regarding similarities and differences within archaeal chaperone machinery in comparison to humans. In the human chaperone network, the UBC protein, a part of ubiquitination system, was the most important module, and interestingly, this system is known to be absent in archaeal organisms. We further compared the chaperone network of archaea with that found in eukaryotic systems, by creating a similar network for Homo sapiens. solfataricus suggested that thermosomes played an integral part of hub proteins in archaeal organisms, where DnaK was absent. Therefore, a similar network was created for another archaeal organism, Sulfolobus solfataricus, a member of Crenarchaeota. However, DnaK protein was present only in a subset of archaeal organisms and absent from many archaea, especially members of Crenarchaeota phylum. ![]() The study revealed that DnaK protein of Hsp70 system acts as hub in protein-protein interaction network. In this study, we attempted such an analysis of chaperone-assisted protein folding in archaeal organisms through network approach using Picrophilus torridus as model system. Very few studies have been ventured into system-level analysis of chaperones and their functioning in archaeal cells. The chaperone machinery of archaeal organisms has been thought to closely resemble that found in humans, at least in terms of constituent players. Molecular chaperones are a diverse group of proteins that ensure proteome integrity by helping the proteins fold correctly and maintain their native state, thus preventing their misfolding and subsequent aggregation.
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