ID   I3_VARV                 Reviewed;         269 AA.
AC   P0DOP4; P33000;
DT   16-OCT-2019, integrated into UniProtKB/Swiss-Prot.
DT   16-OCT-2019, sequence version 1.
DT   23-FEB-2022, entry version 12.
DE   RecName: Full=Protein I3;
GN   ORFNames=I3L, K3L;
OS   Variola virus.
OC   Viruses; Varidnaviria; Bamfordvirae; Nucleocytoviricota; Pokkesviricetes;
OC   Chitovirales; Poxviridae; Chordopoxvirinae; Orthopoxvirus.
OX   NCBI_TaxID=10255;
OH   NCBI_TaxID=9606; Homo sapiens (Human).
RN   [1]
RP   NUCLEOTIDE SEQUENCE [GENOMIC DNA].
RC   STRAIN=Bangladesh-1975;
RX   PubMed=8264798; DOI=10.1038/366748a0;
RA   Massung R.F., Esposito J.J., Liu L.I., Qi J., Utterback T.R., Knight J.C.,
RA   Aubin L., Yuran T.E., Parsons J.M., Loparev V.N., Selivanov N.A.,
RA   Cavallaro K.F., Kerlavage A.R., Mahy B.W.J., Venter J.C.;
RT   "Potential virulence determinants in terminal regions of variola smallpox
RT   virus genome.";
RL   Nature 366:748-751(1993).
RN   [2]
RP   NUCLEOTIDE SEQUENCE [GENOMIC DNA].
RC   STRAIN=Garcia-1966;
RA   Shchelkunov S.N., Chizhikov V.E., Totmenin A.V., Resenchuk S.M.,
RA   Blinov V.M., Sandakhchiev L.S.;
RL   Submitted (DEC-1995) to the EMBL/GenBank/DDBJ databases.
CC   -!- FUNCTION: Single-stranded DNA (ssDNA)-binding phosphoprotein which
CC       stimulates the enzymatic activity of vaccinia ribonucleotide reductase.
CC       In the absence of magnesium and at low I3 concentration, I3 forms
CC       beaded nucleosome-like structures on ssDNA. In the presence of
CC       magnesium and at high I3 concentration, I3 and DNA aggregate into large
CC       branched filamentous structures. Might be essential for viral parental
CC       DNA replication.
CC   -!- SUBUNIT: Homooctamer (Potential). Homoomultimer (Potential). Interacts
CC       with the small subunit of ribonucleotide reductase; this interaction
CC       stimulates ribonucleotide reductase activity. {ECO:0000305}.
CC   -!- SUBCELLULAR LOCATION: Host cytoplasm {ECO:0000305}. Note=Localizes in
CC       cytoplasmic virus factories, where it is associated with viral DNA.
CC       {ECO:0000305}.
CC   -!- INDUCTION: Expressed in the early phase of the viral replicative cycle.
CC   -!- MISCELLANEOUS: This protein is synthesized in the early as well as at
CC       the intermediate time of infection.
CC   -!- SIMILARITY: Belongs to the chordopoxvirinae I3 family. {ECO:0000305}.
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DR   EMBL; L22579; AAA60805.1; -; Genomic_DNA.
DR   EMBL; X76263; CAA53831.1; -; Genomic_DNA.
DR   PIR; G72157; G72157.
DR   PIR; T28495; T28495.
DR   RefSeq; NP_042101.1; NC_001611.1.
DR   GeneID; 1486458; -.
DR   KEGG; vg:1486458; -.
DR   Proteomes; UP000119805; Genome.
DR   GO; GO:0030430; C:host cell cytoplasm; IEA:UniProtKB-SubCell.
DR   GO; GO:0003697; F:single-stranded DNA binding; IEA:InterPro.
DR   GO; GO:0030261; P:chromosome condensation; IEA:UniProtKB-KW.
DR   InterPro; IPR006754; Poxvirus_I3_ssDNA-bd.
DR   Pfam; PF04661; Pox_I3; 1.
DR   PIRSF; PIRSF003767; VAC_I3L; 1.
PE   2: Evidence at transcript level;
KW   DNA condensation; DNA-binding; Early protein; Host cytoplasm.
FT   CHAIN           1..269
FT                   /note="Protein I3"
FT                   /id="PRO_0000448200"
SQ   SEQUENCE   269 AA;  30049 MW;  796A094F74039188 CRC64;
     MSKVIKKRVE TSPRPTASSD SLQTCAGVIE YAKSISKSNA KCIEYVTLNA SQYANCSSIS
     IKLTDSLSSQ MTSTFIMLEG ETKLYKNKSK QDRSDGYFLK IKVTAASPML YQLLEAVYGN
     IKHKERIPNS LHSLLVETIT EKTFKDESIF INKLNGAMVE YVSTGELSIL RSIEGELESL
     SKRERQLAKA IITPVVFYRS GTETKITFAL KKLIIDREVV ANVIGLSGDS ERVSMTENVE
     EDLARNLGLV DIDDEYDEDS DKEKPIFNV