ID   HEXA_MICLU              Reviewed;         143 AA.
AC   O66127;
DT   03-OCT-2012, integrated into UniProtKB/Swiss-Prot.
DT   01-AUG-1998, sequence version 1.
DT   03-AUG-2022, entry version 53.
DE   RecName: Full=Hexaprenyl-diphosphate synthase small subunit ((2E,6E)-farnesyl-diphosphate specific);
DE            Short=HexPS;
DE            EC=2.5.1.83;
DE   AltName: Full=Hexaprenyl diphosphate synthase;
DE   AltName: Full=Hexaprenyl pyrophosphate synthetase;
GN   Name=hexs-a;
OS   Micrococcus luteus (Micrococcus lysodeikticus).
OC   Bacteria; Actinobacteria; Micrococcales; Micrococcaceae; Micrococcus.
OX   NCBI_TaxID=1270;
RN   [1]
RP   NUCLEOTIDE SEQUENCE [GENOMIC DNA], FUNCTION AS A HEXAPRENYL-DIPHOSPHATE
RP   SYNTHASE, CATALYTIC ACTIVITY, AND NOMENCLATURE.
RC   STRAIN=B-P 26;
RX   PubMed=9515931; DOI=10.1128/jb.180.6.1578-1581.1998;
RA   Shimizu N., Koyama T., Ogura K.;
RT   "Molecular cloning, expression, and characterization of the genes encoding
RT   the two essential protein components of Micrococcus luteus B-P 26
RT   hexaprenyl diphosphate synthase.";
RL   J. Bacteriol. 180:1578-1581(1998).
RN   [2]
RP   FUNCTION AS A HEXAPRENYL-DIPHOSPHATE SYNTHASE.
RX   PubMed=7174655; DOI=10.1016/s0021-9258(18)33320-9;
RA   Fujii H., Koyama T., Ogura K.;
RT   "Hexaprenyl pyrophosphate synthetase from Micrococcus luteus B-P 26.
RT   Separation of two essential components.";
RL   J. Biol. Chem. 257:14610-14612(1982).
RN   [3]
RP   FUNCTION AS A HEXAPRENYL-DIPHOSPHATE SYNTHASE.
RC   STRAIN=B-P 26;
RX   PubMed=11514159; DOI=10.1016/s0960-894x(01)00391-2;
RA   Nagaki M., Kimura K., Kimura H., Maki Y., Goto E., Nishino T., Koyama T.;
RT   "Artificial substrates of medium-chain elongating enzymes, hexaprenyl- and
RT   heptaprenyl diphosphate synthases.";
RL   Bioorg. Med. Chem. Lett. 11:2157-2159(2001).
RN   [4]
RP   X-RAY CRYSTALLOGRAPHY (2.40 ANGSTROMS) IN COMPLEX WITH SUBSTRATE ANALOGS
RP   AND MAGNESIUM IONS, REACTION MECHANISM, AND SUBUNIT.
RC   STRAIN=B-P 26;
RX   PubMed=21068379; DOI=10.1074/jbc.m110.147991;
RA   Sasaki D., Fujihashi M., Okuyama N., Kobayashi Y., Noike M., Koyama T.,
RA   Miki K.;
RT   "Crystal structure of heterodimeric hexaprenyl diphosphate synthase from
RT   Micrococcus luteus B-P 26 reveals that the small subunit is directly
RT   involved in the product chain length regulation.";
RL   J. Biol. Chem. 286:3729-3740(2011).
CC   -!- FUNCTION: Catalyzes the condensation of three molecules of isopentenyl
CC       diphosphate with farnesyl diphosphate (FPP) to yield (all-E)-hexaprenyl
CC       diphosphate (HexPP; C30), the precursor of the prenyl side chain of
CC       menaquinone-6. Large subunit Hexs-B catalyzes the condensation reaction
CC       and the final product chain length is cooperatively regulated by both
CC       the Hexs-A and Hexs-B subunits using the whole size of the hydrophobic
CC       cleft as a ruler. {ECO:0000269|PubMed:11514159,
CC       ECO:0000269|PubMed:7174655, ECO:0000269|PubMed:9515931}.
CC   -!- CATALYTIC ACTIVITY:
CC       Reaction=(2E,6E)-farnesyl diphosphate + 3 isopentenyl diphosphate =
CC         all-trans-hexaprenyl diphosphate + 3 diphosphate;
CC         Xref=Rhea:RHEA:27559, ChEBI:CHEBI:33019, ChEBI:CHEBI:58179,
CC         ChEBI:CHEBI:128769, ChEBI:CHEBI:175763; EC=2.5.1.83;
CC         Evidence={ECO:0000269|PubMed:9515931};
CC   -!- SUBUNIT: Dimer of heterodimer or heterotetramer composed of a small
CC       (Hexs-a) and large (Hexs-B) subunit. {ECO:0000269|PubMed:21068379}.
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DR   EMBL; AB003188; BAA25266.1; -; Genomic_DNA.
DR   PDB; 3AQB; X-ray; 2.40 A; A/C=1-143.
DR   PDB; 3AQC; X-ray; 2.61 A; A/C=1-143.
DR   PDBsum; 3AQB; -.
DR   PDBsum; 3AQC; -.
DR   AlphaFoldDB; O66127; -.
DR   SMR; O66127; -.
DR   KEGG; ag:BAA25266; -.
DR   BioCyc; MetaCyc:MON-13828; -.
DR   BRENDA; 2.5.1.83; 3348.
DR   EvolutionaryTrace; O66127; -.
DR   GO; GO:0036423; F:hexaprenyl-diphosphate synthase ((2E,6E)-farnesyl-diphosphate specific) activity; IEA:UniProtKB-EC.
DR   GO; GO:0000287; F:magnesium ion binding; IDA:UniProtKB.
DR   GO; GO:0016765; F:transferase activity, transferring alkyl or aryl (other than methyl) groups; IDA:UniProtKB.
DR   GO; GO:0009234; P:menaquinone biosynthetic process; IEA:UniProtKB-KW.
PE   1: Evidence at protein level;
KW   3D-structure; Menaquinone biosynthesis; Transferase.
FT   CHAIN           1..143
FT                   /note="Hexaprenyl-diphosphate synthase small subunit
FT                   ((2E,6E)-farnesyl-diphosphate specific)"
FT                   /id="PRO_0000419165"
FT   HELIX           2..17
FT                   /evidence="ECO:0007829|PDB:3AQB"
FT   HELIX           28..35
FT                   /evidence="ECO:0007829|PDB:3AQB"
FT   HELIX           41..56
FT                   /evidence="ECO:0007829|PDB:3AQB"
FT   HELIX           57..59
FT                   /evidence="ECO:0007829|PDB:3AQB"
FT   TURN            62..64
FT                   /evidence="ECO:0007829|PDB:3AQB"
FT   HELIX           65..82
FT                   /evidence="ECO:0007829|PDB:3AQB"
FT   TURN            83..87
FT                   /evidence="ECO:0007829|PDB:3AQB"
FT   HELIX           89..110
FT                   /evidence="ECO:0007829|PDB:3AQB"
FT   HELIX           115..126
FT                   /evidence="ECO:0007829|PDB:3AQB"
FT   TURN            127..130
FT                   /evidence="ECO:0007829|PDB:3AQB"
FT   HELIX           131..133
FT                   /evidence="ECO:0007829|PDB:3AQB"
SQ   SEQUENCE   143 AA;  16942 MW;  0D923F9A52BE564B CRC64;
     MRYLHKIELE LNRLTSRYPF FKKIAFDAEI IKLVDDLNVD ENVKCAIVAI DTSMRMQDFI
     NEDNKDSFVL STDVLSALFY KYLSQPFYQH DFLVLTDCVS RINELKSIRA TITDEIALHN
     INKQIHYMFI QPYMNNEKVV SYE