ID   T1SE_ECOLX              Reviewed;         594 AA.
AC   P19705;
DT   01-FEB-1991, integrated into UniProtKB/Swiss-Prot.
DT   01-FEB-1991, sequence version 1.
DT   03-AUG-2022, entry version 72.
DE   RecName: Full=Type I restriction enzyme EcoEI specificity subunit {ECO:0000303|PubMed:2642743};
DE            Short=S protein {ECO:0000303|PubMed:2642743};
DE   AltName: Full=Type I specificity subunit S.EcoEI {ECO:0000303|PubMed:12654995};
DE            Short=S.EcoEI {ECO:0000303|PubMed:12654995};
DE   AltName: Full=Type-1 restriction enzyme EcoEI specificity subunit;
GN   Name=hsdS {ECO:0000303|PubMed:2642743}; Synonyms=hss;
OS   Escherichia coli.
OC   Bacteria; Proteobacteria; Gammaproteobacteria; Enterobacterales;
OC   Enterobacteriaceae; Escherichia.
OX   NCBI_TaxID=562;
RN   [1]
RP   NUCLEOTIDE SEQUENCE [GENOMIC DNA], FUNCTION, RECOGNITION SITE, AND DOMAIN.
RC   STRAIN=A58;
RX   PubMed=2642743; DOI=10.1016/0092-8674(89)90988-4;
RA   Cowan G.M., Gann A.A.F., Murray N.E.;
RT   "Conservation of complex DNA recognition domains between families of
RT   restriction enzymes.";
RL   Cell 56:103-109(1989).
RN   [2]
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 two adenine
CC       residues of the sequence 5'-GAGN(7)ATGC-3'. In the presence of the R
CC       subunit the complex can also act as an endonuclease, binding to the
CC       same target sequence but cutting the DNA some distance from this site.
CC       Whether the DNA is cut or modified depends on the methylation state of
CC       the target sequence. When the target site is unmodified, the DNA is
CC       cut. When the target site is hemimethylated, the complex acts as a
CC       maintenance MTase modifying the DNA so that both strands become
CC       methylated (PubMed:2642743, PubMed:12654995). After locating a non-
CC       methylated recognition site, the enzyme complex serves as a molecular
CC       motor that translocates DNA in an ATP-dependent manner until a
CC       collision occurs that triggers cleavage (By similarity).
CC       {ECO:0000250|UniProtKB:P05719, ECO:0000269|PubMed:2642743,
CC       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
CC       sequence. {ECO:0000269|PubMed:2642743}.
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; J03162; AAA23986.1; -; Genomic_DNA.
DR   PIR; B32343; NDECES.
DR   AlphaFoldDB; P19705; -.
DR   IntAct; P19705; 11.
DR   REBASE; 3643; S.EcoEI.
DR   PRIDE; P19705; -.
DR   PRO; PR:P19705; -.
DR   GO; GO:0003677; F:DNA binding; IEA:UniProtKB-KW.
DR   GO; GO:0009307; P:DNA restriction-modification system; IEA:UniProtKB-KW.
DR   Gene3D; 3.90.220.20; -; 2.
DR   InterPro; IPR000055; Restrct_endonuc_typeI_TRD.
DR   InterPro; IPR044946; Restrct_endonuc_typeI_TRD_sf.
DR   Pfam; PF01420; Methylase_S; 2.
PE   3: Inferred from homology;
KW   DNA-binding; Restriction system.
FT   CHAIN           1..594
FT                   /note="Type I restriction enzyme EcoEI specificity subunit"
FT                   /id="PRO_0000198034"
SQ   SEQUENCE   594 AA;  66344 MW;  3D4BF0345226CF63 CRC64;
     MAVEKLITDH IDIWSSALQT RSMAGRGSNG KIDLYGIKKL RELILELAVR GKLVPQDPND
     EPASELLKRI AAEKTELVKQ GKIKKQKPLL RISEDEKPFE LPEGWEWITL SEIATINPKI
     EVTDDEQEIS FVPMPCISTR FDGAHDQEIK KWGEVKKGYT HFADGDIALA KITPCFENSK
     AVIFKGLKGG VGVGTTELHV ARPISSELNL QYILLNIKSP HYLSMGESMM TGSAGQKRVP
     RSFFENYPIP FPPNTEQARI VGTFSKLMFL CDQLEQQSLT SLDAHQQLVE TLLATLTDSQ
     NAEELAENWA RISQYFDTLF TTEASIDALK QTILQLAVMG KLVSQDPNDE PASELLKRVE
     QEKVQLVKEG KIKKQKPLPP VSDDEKPFEL PIGWEWCRIG EIIANMDAGW SPACSPEPSP
     NEDIWGVLKT TAVQSLEYRE QENKTLPNSK LPRPQYEVHD GDILVTRAGP KNRVGVSCLV
     EKTRSKLMIS DKIIRFHLIS DDISAKYISL CLNRGVTADY LEASKSGMAE SQMNISQENL
     RSAPIALPPT AIQLKVISTI EDFFKVCDQL KSRLQSAQQT QLHLADALTD AALN