In this task, you're given a paragraph from the research paper and your task is to generate a suitable title for the research paper based on the given paper. Under 100 words is a good title length.

Ca 2+ is one of the most universal and versatile signaling molecules and is involved in almost every aspect of cellular processes. Viruses are adept at utilizing the universal Ca 2+ signal to create a tailored cellular environment that meets their own demands. This review summarizes most of the known mechanisms by which viruses perturb Ca 2+ homeostasis and utilize Ca 2+ and cellular Ca 2+ -binding proteins to their benefit in their replication cycles. Ca 2+ plays important roles in virion structure formation, virus entry, viral gene expression, posttranslational processing of viral proteins and virion maturation and release. As part of the review, we introduce an algorithm to identify linear "EF-hand" Ca 2+ -binding motifs which resulted in the prediction of a total of 93 previously unrecognized Ca 2+ -binding motifs in virus proteins. Many of these proteins are nonstructural proteins, a class of proteins among which Ca 2+ interactions had not been formerly appreciated. The presence of linear Ca 2+ -binding motifs in viral proteins enlarges the spectrum of Ca 2+ -virus interplay and expands the total scenario of viral calciomics. (J.J. Yang). for structural integrity or functionality; and (3) critical virus-host interactions depend on cellular Ca 2+ -regulated proteins or pathways. This review, which aims to stimulate future studies on the roles of Ca 2+ in virus infection, is focused on such interplay by highlighting recent discoveries in the biological roles of Ca 2+ in virus infection. 0143-4160/$ -see front matter
Viral calciomics: Interplays between Ca 2+ and virus

In the present studies , we report the cloning and structural characterization of the HFGL2 gene and its functional role in human fulminant hepatitis. The HFGL2 gene is approximately 7 kb in length with 2 exons. The putative promoter contains cis element consensus sequences that strongly suggest the inducibility of its expression. From the nucleotide sequence of the human gene , a 439-amino acid long protein is predicted. The overall identity between the murine fgl2 and hfgl2 coded proteins is over 70%. About 225 amino acids at the carboxyl end of these molecules are almost 90% identical , and correspond to a well-conserved fibrinogen-related domain. Both HFGL2 and FGL2 encode a type II transmembrane protein with a predicted catalytic domain toward the amino terminus of the protein. Transient transfection of Chinese hamster ovary (CHO) cells with a fulllength cDNA of HFGL2 coding region resulted in high levels of prothrombinase activity. Livers from 8 patients transplanted for fulminant viral hepatitis were examined for extent of necrosis , inflammation, fibrin deposition , and HFGL2 induction. In situ hybridization showed positive staining of macrophages in areas of active hepatocellular necrosis. Fibrin stained positively in these areas and was confirmed by electron microscopy. These studies define a unique prothrombinase gene (HFGL2) and implicate its importance in the pathogenesis of fulminant viral hepatitis.
Molecular and Functional Analysis of the Human Prothrombinase Gene (HFGL2) and Its Role in Viral Hepatitis

Membrane fusion is not spontaneous. Therefore, enveloped viruses have evolved membrane-fusion mediating glycoproteins that, once activated, refold, and release energy that fuses viral and cellular membranes. The influenza A virus hemagglutinin (HA) protein is a prototypic structural class I viral fusion glycoprotein that, once primed by proteolytic cleavage, is activated by endosomal low pH to form a fusogenic ''leash-in-grooves'' hairpin structure. Low-pH induced HA protein refolding is an irreversible process, so acid exposure in the absence of a target membrane leads to virus inactivation. The HA proteins of diverse influenza virus subtypes isolated from a variety of species differ in their acid stabilities, or pH values at which irreversible HA protein conformational changes are triggered. Recently, efficient replication of highly pathogenic avian influenza (HPAI) viruses such as H5N1 in avian species has been associated with a relatively high HA activation pH. In contrast, a decrease in H5N1 HA activation pH has been shown to enhance replication and airborne transmission in mammals. Mutations that alter the acid stabilities of H1 and H3 HA proteins have also been discovered that influence the amantadine susceptibilities, replication rates, and pathogenicities of human influenza viruses. An understanding of the role of HA acid stability in influenza virus biology is expected to aid in identifying emerging viruses with increased pandemic potential and assist in developing live attenuated virus vaccines. Acid-induced HA protein activation, which has provided a paradigm for protein-mediated membrane fusion, is now identified as a novel determinant of influenza virus biology. Abbreviations Cytoplasmic tail ER

Acid-Induced Membrane Fusion by the Hemagglutinin Protein and Its Role in Influenza Virus Biology Endoplasmic reticulum HA Hemagglutinin