A new set of hydrophilicity high-performance liquid chromatography (HPLC) parameters is presented. These parameters were derived from the retention times of 20 model synthetic peptides, Ac-Gly-X-X-(Leu)3-(Lys)2-amide, where X was substituted with the 20 amino acids found in proteins. Since hydrophilicity parameters have been used extensively in algorithms to predict which amino acid residues are antigenic, we have compared the profiles generated by our new set of hydrophilic HPLC parameters on the same scale as nine other sets of parameters. Generally, it was found that the HPLC parameters obtained in this study correlated best with antigenicity. In addition, it was shown that a combination of the three best parameters for predicting antigenicity further improved the predictions. These predicted surface sites or, in other words, the hydrophilic, accessible, or mobile regions were then correlated to the known antigenic sites from immunological studies and accessible sites determined by X-ray crystallographic data for several proteins.
Calreticulin is an endoplasmic reticulum (ER) luminalmutant revealed that conformation changes in calreticulin mutant may be responsible for the loss of its chaperone activity. We conclude that mutation of a single amino acid residue in calreticulin has devastating consequences for its chaperone function, indicating that mutations in chaperones may play a significant role in protein folding disorders.The endoplasmic reticulum (ER) 1 plays an essential role in a variety of cellular processes, including Ca 2ϩ homeostasis, protein and lipid synthesis, and post-translational modification and folding of membrane-associated and secreted proteins (1). The ER ensures that only correctly folded proteins proceed through the secretory pathway and directs misfolded proteins to ER-associated degradation (2, 3). The lumen of the ER is a dynamic environment that contains numerous molecular chaperones and Ca 2ϩ -binding proteins that are designed for these tasks. Molecular chaperones are proteins that bind to misfolded/unfolded proteins in a transient manner to assist in their folding.Calreticulin is a Ca 2ϩ -binding chaperone that resides in the lumen of the ER and is involved in modulation of Ca 2ϩ homeostasis and in the folding of newly synthesized glycoproteins via the "calreticulin-calnexin cycle" (4 -7). Calreticulin and calnexin are both ER lectins, which bind transiently to virtually all newly synthesized glycoproteins (5-7). Chaperone-assisted protein folding has been studied extensively using Escherichia coli GroEL heat shock proteins, which are cytoplasmic (8). Numerous studies have been carried out on ER-associated chaperones (2-7); yet, the molecular features of calreticulin that confer its chaperone function have not yet been determined (7).Three distinct structural domains have been identified in calreticulin: the amino-terminal, globular N-domain; the central P-domain; and the carboxyl-terminal C-domain (7). NMR (9), modeling (10), and biochemical studies (11) indicate that the globular N-domain and the "extended arm" P-domain of calreticulin may form a functional protein-folding unit (10). This region of calreticulin contains a Zn 2ϩ binding site and one disulfide bond, and it may also bind ATP (12)(13)(14). When calreticulin binds Zn 2ϩ , it undergoes dramatic conformational changes (15). Chemical modification of calreticulin has revealed that four histidines located in the N-domain of the protein (His 25 , His 82 , His 128 , and His 153 ) are involved in the Zn 2ϩ binding (12). The Zn 2ϩ -dependent conformational change in calreticulin affects its ability to bind to unfolded protein/ glycoprotein substrates in vitro (16), suggesting that conformational changes in calreticulin may modify its chaperone function. The role of the Zn 2ϩ binding histidine residues in calreticulin function is not known.Calreticulin deficiency is embryonic lethal, and cells derived from calreticulin knockout embryos have impaired Ca 2ϩ homeostasis and compromised protein folding and quality control (11,17). The availability of calret...
Calreticulin is a Ca
2؉-binding chaperone that resides in the lumen of the endoplasmic reticulum and is involved in the regulation of intracellular Ca 2؉ homeostasis and in the folding of newly synthesized glycoproteins. In this study, we have used site-specific mutagenesis to map amino acid residues that are critical in calreticulin function.
Congenital malformations in sub-Saharan Africa-warnings of a silent epidemic?SARS-CoV-2 has tragically shown the cost of a global pandemic. Only a few years earlier, the outbreak of Zika virus in Brazil and elsewhere in South America caught the international community by surprise. There was no epidemiological surveillance for Zika virus established at the time, since the African-origin virus was previously
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.