DNA-packaging protein gp3 (terminase small subunit) is involved in DNA packing in bacteriophage. It contains a channel where DNA is bound and passed to DNA-packaging protein gp2 (terminase large subunit) [].
Initiation of packaging of double-stranded viral DNA involves the specific interaction of the prohead with viral DNA in a process mediated by a phage-encoded terminase protein. The terminase enzymes are usually hetero-oligomers composed of a small and a large subunit [, ]. This entry represents the C-terminal domain of the large subunit.Proteins containing this domain include gp2 from Bacillus phage SPP1 [, ].
This entry represents RNA polymerase inhibitor, including Gp2 from T7-like viruses. Bacterial RNA polymerase inhibitor, which is expressed in the late stage of lytic development, is also essential for continuous synthesis of phage DNA and functions in the packaging of the viral genome into the mature phage particle []. It inhibits the bacterial host RNA polymerase by interacting with the RpoC subunit and inhibiting the formation of a promoter complex [, , ].
The class F scavenger receptor 1 (SCARF1/SREC-I) contains epidermal growth factor (EGF)-like repeats in its extracellular domain, followed by a long C-terminal cytoplasmic tail composed of serine and proline-rich regions. SCARF1 is an endocytic receptor for acetylated low density lipoprotein, HSP70, HSP90, calreticulin, gp96, and GP2 [, , , , ]. Dendritic cells (DCs),macrophages and endothelial cells use SCARF1 to recognize and engulf apoptotic cells via the complement component C1q; this mediates apoptotic cells clearance, antigen clearance and prevents autoimmunity [].
This group of sequences represent a highly divergent family of the large subunit of phage terminase. All members are encoded by phage genomes or within prophage regions of bacterial genomes. This is a distinct family from the phage terminase family represented by .Initiation of packaging of double-stranded viral DNA involves the specific interaction of the prohead with viral DNA in a process mediated by a phage-encoded terminase protein. The terminase are usually hetero-oligomers composed of a small and a large subunit [, ]. This entry includes the large subunit, including GP2 from Bacillus phage SPP1 [, ].
This entry represents the N-terminal domain of the large subunit of the terminase protein.Initiation of packaging of double-stranded viral DNA involves the specific interaction of the prohead with viral DNA in a process mediated by a phage-encoded terminase protein. The terminase enzymes are usually hetero-oligomers composed of a small and a large subunit. This region possess an endonuclease and ATPase activity that require Mg2+ and a neutral or slightly basic reaction. This region is also found in bacterial sequences [, ].Proteins containing this domain include gp2 from Bacillus phage SPP1 [, ].
This entry represents RNA polymerase inhibitor, including Gp2 from T7-like viruses. Bacterial RNA polymerase inhibitor, which is expressed in the late stage of lytic development, is also essential for continuous synthesis of phage DNA and functions in the packaging of the viral genome into the mature phage particle []. It inhibits the bacterial host RNA polymerase by interacting with the RpoC subunit and inhibiting the formation of a promoter complex [, , ].Gp2 folds into a compact globular domain consisting of a three-stranded beta sheet that packs against an α-helix with a beta1beta2alpha1beta3 topology. The central beta2 strand is flanked by antiparallel beta1 and beta3 strands. Positive and negative charges are at opposite sides on the surface of the molecule. Two conserved arginine residues located on one side are important for binding to and inhibition of host RNA polymerase [].
The class F scavenger receptors (SCARFs or SRECs) have two isoforms, SCARF1/SREC-I and SCARF2/SREC-II. Similar to SREC-I, SREC-II contains multiple epidermal growth factor-like repeats in its extracellular domain. However, in contrast to SREC-I, SREC-II had little activity to internalize modified low density lipoproteins (LDL). SREC-II and SREC-I display strong heterophilic trans-interaction through the extracellular domains []. They are expressed in a specific temporal and spatial pattern during epidermal development [].Mutations in the SCARF2 gene cause Van den Ende-Gupta syndrome (VDEGS), a syndrome characterised by craniofacial and skeletal abnormalities []. The class F scavenger receptor 1 (SCARF1/SREC-I) contains epidermal growth factor (EGF)-like repeats in its extracellular domain, followed by a long C-terminal cytoplasmic tail composed of serine and proline-rich regions. SCARF1 is an endocytic receptor for acetylated low density lipoprotein, HSP70, HSP90, calreticulin, gp96, and GP2 [, , , , ]. Dendritic cells (DCs), macrophages and endothelial cells use SCARF1 to recognize and engulf apoptotic cells via the complement component C1q; this mediates apoptotic cells clearance, antigen clearance and prevents autoimmunity [].
Proteins in this family include the envelope glycoprotein and the pre-small/secreted glycoprotein from Filoviridae []. The envelope glycoprotein can be cleaved into 3 chains: GP1, GP2 and GP2-delta.GP1 is responsible for binding to the receptor(s), such as CD209 and CLEC4M, on target cells. These interactions not only facilitate virus cell entry, but also allow capture of viral particles by dendritic cells (DCs) and subsequent transmission to susceptible cells without DCs infection (trans infection) [].GP2 acts as a class I viral fusion protein. It is responsible for penetration of the virus into the cell cytoplasm by mediating the fusion of the membrane of the endocytosed virus particle with the endosomal membrane []. GP1,2 peplomers mediates endothelial cell activation and decreases endothelial barrier function. It mediates activation of primary macrophages. At terminal stages of the viral infection, when its expression is high, GP1,2 down-modulates the expression of various host cell surface molecules that are essential for immune surveillance and cell adhesion [].GP2delta is part of the complex GP1,2delta released by host ADAM17 metalloprotease. This secreted complex may play a role in the pathogenesis of the virus by efficiently blocking the neutralizing antibodies that would otherwise neutralize the virus surface glycoproteins GP1,2. Might therefore contribute to the lack of inflammatory reaction seen during infection in spite the of extensive necrosis and massive virus production. GP1,2delta does not seem to be involved in activation of primary macrophage [].pre-small/secreted glycoprotein sGP seems to possess an anti-inflammatory activity as it can reverse the barrier-decreasing effects of TNF alpha. It might therefore contribute to the lack of inflammatory reaction seen during infection in spite the of extensive necrosis and massive virus production. It does not seem to be involved in activation of primary macrophages. It does not seem to interact specifically with neutrophils [, , , ].
