ID   TERS_BPSPP              Reviewed;         147 AA.
AC   P54307; Q1EJR9;
DT   01-OCT-1996, integrated into UniProtKB/Swiss-Prot.
DT   16-SEP-2015, sequence version 4.
DT   03-AUG-2022, entry version 93.
DE   RecName: Full=Terminase small subunit;
DE   AltName: Full=G1P;
DE   AltName: Full=Terminase, small subunit gp1;
GN   Name=1;
OS   Bacillus phage SPP1 (Bacteriophage SPP1).
OC   Viruses; Duplodnaviria; Heunggongvirae; Uroviricota; Caudoviricetes;
OC   Caudovirales; Siphoviridae.
OX   NCBI_TaxID=10724;
OH   NCBI_TaxID=1423; Bacillus subtilis.
RN   [1]
RP   NUCLEOTIDE SEQUENCE [GENOMIC DNA].
RX   PubMed=1548711; DOI=10.1016/0022-2836(92)90578-8;
RA   Chai S., Bravo A., Lueder G., Nedlin A., Trautner T.A., Alonso J.C.;
RT   "Molecular analysis of the Bacillus subtilis bacteriophage SPP1 region
RT   encompassing genes 1 to 6. The products of gene 1 and gene 2 are required
RT   for pac cleavage.";
RL   J. Mol. Biol. 224:87-102(1992).
RN   [2]
RP   NUCLEOTIDE SEQUENCE [GENOMIC DNA], AND PROTEIN SEQUENCE OF 2-26 AND 64-91.
RX   PubMed=8030254; DOI=10.1006/viro.1994.1415;
RA   Chai S., Kruft V., Alonso J.C.;
RT   "Analysis of the Bacillus subtilis bacteriophages SPP1 and SF6 gene 1
RT   product: a protein involved in the initiation of headful packaging.";
RL   Virology 202:930-939(1994).
RN   [3]
RP   NUCLEOTIDE SEQUENCE [LARGE SCALE GENOMIC DNA].
RX   PubMed=9434185; DOI=10.1016/s0378-1119(97)00547-7;
RA   Alonso J.C., Luder G., Stiege A.C., Chai S., Weise F., Trautner T.A.;
RT   "The complete nucleotide sequence and functional organization of Bacillus
RT   subtilis bacteriophage SPP1.";
RL   Gene 204:201-212(1997).
RN   [4]
RP   NUCLEOTIDE SEQUENCE [GENOMIC DNA].
RA   Benini S., Chechik M., Ortiz-Lombardia M., Polier S., Shevtsov M.B.,
RA   De Luchi D., Alonso J.C., Antson A.A.;
RT   "The DNA-binding domain of bacteriophage SF6 small terminase subunit.";
RL   Submitted (MAY-2006) to the EMBL/GenBank/DDBJ databases.
RN   [5]
RP   FUNCTION.
RX   PubMed=12697751; DOI=10.1074/jbc.m301805200;
RA   Camacho A.G., Gual A., Lurz R., Tavares P., Alonso J.C.;
RT   "Bacillus subtilis bacteriophage SPP1 DNA packaging motor requires
RT   terminase and portal proteins.";
RL   J. Biol. Chem. 278:23251-23259(2003).
RN   [6]
RP   REVIEW.
RX   PubMed=23419885; DOI=10.1016/j.virusres.2013.01.021;
RA   Oliveira L., Tavares P., Alonso J.C.;
RT   "Headful DNA packaging: bacteriophage SPP1 as a model system.";
RL   Virus Res. 173:247-259(2013).
CC   -!- FUNCTION: The terminase small subunit specifically recognizes the non-
CC       adjacent pacL and pacR packaging subsites and regulates the ATPase
CC       activity of the terminase large subunit. The terminase lies at a unique
CC       vertex of the procapsid and is composed of two subunits, a small
CC       terminase subunit involved in viral DNA recognition (packaging
CC       sequence), and a large terminase subunit possessing endonucleolytic and
CC       ATPase activities. Both terminase subunits heterooligomerize and are
CC       docked on the portal protein to form the packaging machine. The
CC       terminase large subunit exhibits endonuclease activity and cleaves the
CC       viral genome concatemer once the capsid is full (headful packaging).
CC       Once the capsid is packaged with the DNA, the terminase complex is
CC       substituted by neck proteins. {ECO:0000305|PubMed:12697751}.
CC   -!- SUBUNIT: Homodecamer. Interacts with the terminase large subunit gp2;
CC       the active complex is probably composed of a one monomer of gp2 and two
CC       or more decamers of gp1. {ECO:0000305|PubMed:12697751}.
CC   -!- ALTERNATIVE PRODUCTS:
CC       Event=Alternative initiation; Named isoforms=2;
CC       Name=G1P;
CC         IsoId=P54307-1; Sequence=Displayed;
CC       Name=G1P*;
CC         IsoId=P54307-2; Sequence=VSP_018686;
CC   -!- SIMILARITY: Belongs to the SPP1-like small terminase family.
CC       {ECO:0000305}.
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DR   EMBL; X56064; CAA39536.1; ALT_SEQ; Genomic_DNA.
DR   EMBL; X97918; CAA66571.1; ALT_SEQ; Genomic_DNA.
DR   EMBL; AM268239; CAK29440.1; -; Genomic_DNA.
DR   PIR; S24450; S24450.
DR   RefSeq; NP_690652.1; NC_004166.2.
DR   SMR; P54307; -.
DR   GeneID; 955251; -.
DR   KEGG; vg:955251; -.
DR   Proteomes; UP000002559; Genome.
DR   GO; GO:0003677; F:DNA binding; IEA:UniProtKB-KW.
DR   GO; GO:0051276; P:chromosome organization; IEA:InterPro.
DR   Gene3D; 1.10.10.1400; -; 1.
DR   InterPro; IPR038713; Terminase_Gp1_N_sf.
DR   InterPro; IPR005335; Terminase_ssu.
DR   Pfam; PF03592; Terminase_2; 1.
PE   1: Evidence at protein level;
KW   Alternative initiation; Direct protein sequencing; DNA-binding;
KW   Reference proteome; Viral genome packaging; Viral release from host cell.
FT   INIT_MET        1
FT                   /note="Removed; by host"
FT                   /evidence="ECO:0000269|PubMed:8030254"
FT   CHAIN           2..147
FT                   /note="Terminase small subunit"
FT                   /id="PRO_0000003378"
FT   VAR_SEQ         1..63
FT                   /note="Missing (in isoform G1P*)"
FT                   /evidence="ECO:0000305"
FT                   /id="VSP_018686"
SQ   SEQUENCE   147 AA;  16334 MW;  6C0D4932CDDAE520 CRC64;
     MGEVKGKWTP KLERFVDEYF INGMNATKAA IAAGYSKKSA STIAAENMQK PHVRARIEER
     LAQMDKKRIM QAEEVLEHLT RIALGQEKEQ VLMGIGKGAE TKTHVEVSAK DRIKALELLG
     KAHAVFTDKQ KVETNQVIIV DDSGDAE