ID   T1S_SALPO               Reviewed;         463 AA.
AC   P07990;
DT   01-AUG-1988, integrated into UniProtKB/Swiss-Prot.
DT   01-AUG-1988, sequence version 1.
DT   27-MAR-2024, entry version 66.
DE   RecName: Full=Type I restriction enzyme StySPI specificity subunit {ECO:0000303|PubMed:3025838};
DE            Short=S protein {ECO:0000303|PubMed:3025838};
DE   AltName: Full=Type I restriction and modification system SP {ECO:0000303|PubMed:3025838};
DE   AltName: Full=Type I specificity subunit S.StySPI {ECO:0000303|PubMed:12654995};
DE            Short=S.StySPI {ECO:0000303|PubMed:12654995};
DE   AltName: Full=Type-1 restriction enzyme StySPI specificity subunit;
GN   Name=hsdS {ECO:0000303|PubMed:3025838};
OS   Salmonella potsdam.
OC   Bacteria; Pseudomonadota; Gammaproteobacteria; Enterobacterales;
OC   Enterobacteriaceae; Salmonella.
OX   NCBI_TaxID=597;
RN   [1]
RP   NUCLEOTIDE SEQUENCE [GENOMIC DNA], FUNCTION, AND DOMAIN.
RX   PubMed=3025838; DOI=10.1073/pnas.83.24.9368;
RA   Fuller-Pace F.V., Murray N.E.;
RT   "Two DNA recognition domains of the specificity polypeptides of a family of
RT   type I restriction enzymes.";
RL   Proc. Natl. Acad. Sci. U.S.A. 83:9368-9372(1986).
RN   [2]
RP   DOMAIN.
RX   PubMed=2838725; DOI=10.1111/j.1365-2958.1987.tb00521.x;
RA   Gann A.A.F., Campbell A.J.B., Collins J.F., Coulson A.F.W., Murray N.E.;
RT   "Reassortment of DNA recognition domains and the evolution of new
RT   specificities.";
RL   Mol. Microbiol. 1:13-22(1987).
RN   [3]
RP   NOMENCLATURE.
RX   PubMed=12654995; DOI=10.1093/nar/gkg274;
RA   Roberts R.J., Belfort M., Bestor T., Bhagwat A.S., Bickle T.A.,
RA   Bitinaite J., Blumenthal R.M., Degtyarev S.K., Dryden D.T., Dybvig K.,
RA   Firman K., Gromova E.S., Gumport R.I., Halford S.E., Hattman S.,
RA   Heitman J., Hornby D.P., Janulaitis A., Jeltsch A., Josephsen J., Kiss A.,
RA   Klaenhammer T.R., Kobayashi I., Kong H., Krueger D.H., Lacks S.,
RA   Marinus M.G., Miyahara M., Morgan R.D., Murray N.E., Nagaraja V.,
RA   Piekarowicz A., Pingoud A., Raleigh E., Rao D.N., Reich N., Repin V.E.,
RA   Selker E.U., Shaw P.C., Stein D.C., Stoddard B.L., Szybalski W.,
RA   Trautner T.A., Van Etten J.L., Vitor J.M., Wilson G.G., Xu S.Y.;
RT   "A nomenclature for restriction enzymes, DNA methyltransferases, homing
RT   endonucleases and their genes.";
RL   Nucleic Acids Res. 31:1805-1812(2003).
CC   -!- FUNCTION: The specificity (S) subunit of a type I restriction enzyme;
CC       this subunit dictates DNA sequence specificity. The M and S subunits
CC       together form a methyltransferase (MTase) that methylates A-2 on the
CC       top strand and A-3 on the bottom strand of the sequence 5'-AACN(6)GTRC-
CC       3'. In the presence of the R subunit the complex can also act as an
CC       endonuclease, binding to the same target sequence but cutting the DNA
CC       some distance from this site. Whether the DNA is cut or modified
CC       depends on the methylation state of the target sequence. When the
CC       target site is unmodified, the DNA is cut. When the target site is
CC       hemimethylated, the complex acts as a maintenance MTase modifying the
CC       DNA so that both strands become methylated (PubMed:3025838,
CC       PubMed:12654995). After locating a non-methylated recognition site, the
CC       enzyme complex serves as a molecular motor that translocates DNA in an
CC       ATP-dependent manner until a collision occurs that triggers cleavage
CC       (By similarity). {ECO:0000250|UniProtKB:P05719,
CC       ECO:0000269|PubMed:3025838, ECO:0000303|PubMed:12654995}.
CC   -!- SUBUNIT: The type I restriction/modification system is composed of
CC       three polypeptides R, M and S; the restriction enzyme has stoichiometry
CC       R(2)M(2)S(1) while the methyltransferase is M(2)S(1).
CC       {ECO:0000250|UniProtKB:P05719}.
CC   -!- DOMAIN: Contains two DNA recognition domains, each specifying
CC       recognition of one of the two defined components of the target sequence
CC       (PubMed:3025838). The recognition domains can be exchanged between
CC       different S proteins, generating enzymes that have new sequence
CC       specificities (PubMed:2838725). {ECO:0000269|PubMed:2838725,
CC       ECO:0000269|PubMed:3025838}.
CC   -!- MISCELLANEOUS: Type I restriction and modification enzymes are complex,
CC       multifunctional systems which require ATP, S-adenosyl methionine and
CC       Mg(2+) as cofactors and, in addition to their endonucleolytic and
CC       methylase activities, are potent DNA-dependent ATPases.
CC       {ECO:0000250|UniProtKB:P05719}.
CC   -!- SIMILARITY: Belongs to the type-I restriction system S methylase
CC       family. {ECO:0000305}.
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DR   EMBL; M14984; AAA27145.1; -; Genomic_DNA.
DR   AlphaFoldDB; P07990; -.
DR   SMR; P07990; -.
DR   REBASE; 3689; S.StySPI.
DR   PRO; PR:P07990; -.
DR   GO; GO:0003677; F:DNA binding; IEA:UniProtKB-KW.
DR   GO; GO:0009307; P:DNA restriction-modification system; IEA:UniProtKB-KW.
DR   CDD; cd17252; RMtype1_S_EcoKI-TRD1-CR1_like; 1.
DR   CDD; cd17523; RMtype1_S_StySPI-TRD2-CR2_like; 1.
DR   Gene3D; 3.90.220.20; DNA methylase specificity domains; 2.
DR   InterPro; IPR000055; Restrct_endonuc_typeI_TRD.
DR   InterPro; IPR044946; Restrct_endonuc_typeI_TRD_sf.
DR   PANTHER; PTHR43140:SF1; TYPE I RESTRICTION ENZYME ECOKI SPECIFICITY SUBUNIT; 1.
DR   PANTHER; PTHR43140; TYPE-1 RESTRICTION ENZYME ECOKI SPECIFICITY PROTEIN; 1.
DR   Pfam; PF01420; Methylase_S; 2.
DR   SUPFAM; SSF116734; DNA methylase specificity domain; 2.
PE   3: Inferred from homology;
KW   DNA-binding; Restriction system.
FT   CHAIN           1..463
FT                   /note="Type I restriction enzyme StySPI specificity
FT                   subunit"
FT                   /id="PRO_0000198038"
SQ   SEQUENCE   463 AA;  51190 MW;  1C42A1717F1E85CF CRC64;
     MNRGKLPEGW ATAPVSTVTT LIRGVTYKKE QALNYLQDDY LPIIRANNIQ NGKFDTTDLV
     FVPKNLVKES QKISPEDIVI AMSSGSKSVV GKSAHQRLPF ECSFGAFCGA LRPEKFISPN
     YIAHFTKSSF YRNKISSLSA GANINNIKPA SFDLINIPIP SLAEQKIIAE KLDTLLAQVD
     STKARLEQIP QILKRFRQAV LAAAVSGTLT TALRNSHSLI GWHSTNLGAL IVDSCNGLAK
     RQGLNGNEIT ILRLADFKDA QRIIGNERKI KLDSKEENKY SLENDDILVI RVNGSADLAG
     RFIEYKSNGD IEGFCDHFIR LRLDSNKIMS RFLTYIANEG EGRFYLRNSL STSAGQNTIN
     QTSIKGLSFL LPPLKEQAEI VRRVEQLFAY ADTIEKQVNN ALTRVNSLTQ SILAKAFRGE
     LTAQWRAENP DLISGKNSAA ALLEKIKAER AVSGGKKTSR KKA
//