Escherichia coli Migula (bacterium) K-12 MG1655 [ECO]

FULL NAME: DNA polymerase I


DESCRIPTION:
DNA polymerase I (Pol I) is primarily a repair enzyme, although it also has a function in replication. About 400 Pol I molecules exist in a single bacterium. DNA polymerase I only makes an average of 20 phosphodiester bonds before dissociating from the template. These properties make good sense for an enzyme that is going to replace damaged DNA. Damage occurs at separate locations so the large number of Pol I molecules means that a repair enzyme is always close at hand. In addition to polymerase activity, this DNA polymerase exhibits 3' to 5' and 5' to 3' exonuclease activity. It is able to utilize nicked circular duplex DNA as a template and can unwind the parental DNA strand from its template. DNA polymerase I has nucleolytic (depolymerizing) activities, which are an intimate part of their function. The 5′ to 3′ exonuclease activity removes base-paired sequences ahead of the polymerizing activity. During replication, this can remove primers ahead of the polymerizing function of the DNA polymerase. Another intimate function of DNA polymerase I (and of the other forms of DNA polymerase found in E. coli) is the 3′ to 5′ exonuclease activity. This activity can de-polymerize DNA starting from the newly synthesized end. Imagining why DNA polymerase would have an activity that opposes the action of the enzyme is a little difficult. The 3′ to 5′ exonuclease activity serves an editing function to ensure the fidelity of replication. Suppose DNA polymerase were to make a mistake and add a T opposite a G in the template strand. When the enzyme begins the next step of polymerization, the T is not properly paired with the template. The 3′ to 5′ exonucleolytic activity of DNA polymerase then removes the unpaired nucleotide, releasing TMP, until a properly paired stretch is detected. Then polymerization can resume. This cycle costs two high-energy phosphate bonds because TTP is converted to TMP. While this may seem wasteful of energy, the editing process does keep the information store of the cell intact.

STRUCTURE SIMILARITY:
Belongs to the DNA polymerase type-A family.
Contains 1 5'-3' exonuclease domain.
Contains 1 3'-5' exonuclease domain.


SUBUNIT STRUCTURE:
Single-chain monomer with multiple functions.


CATALYTIC ACTIVITY:
Deoxynucleoside triphosphate + DNA(n) = diphosphate + DNA(n+1).


PROTEIN TYPE(S):
A-family DNA polymerase
5'-3' exonuclease
3'-5' exonuclease
dRP-lyase


RELATED PATHWAY(S):
DNA replication
base excision repair (BER)
nucleotide excision repair (NER)
homologous recombination (HR)


RELATED DAMAGE:
5'-P end
5'-dRP termini


Amino acids sequence

        10         20         30         40         50         60
MVQIPQNPLI LVDGSSYLYR AYHAFPPLTN SAGEPTGAMY GVLNMLRSLI MQYKPTHAAV
        70         80         90        100        110        120
VFDAKGKTFR DELFEHYKSH RPPMPDDLRA QIEPLHAMVK AMGLPLLAVS GVEADDVIGT
       130        140        150        160        170        180
LAREAEKAGR PVLISTGDKD MAQLVTPNIT LINTMTNTIL GPEEVVNKYG VPPELIIDFL
       190        200        210        220        230        240
ALMGDSSDNI PGVPGVGEKT AQALLQGLGG LDTLYAEPEK IAGLSFRGAK TMAAKLEQNK
       250        260        270        280        290        300
EVAYLSYQLA TIKTDVELEL TCEQLEVQQP AAEELLGLFK KYEFKRWTAD VEAGKWLQAK
       310        320        330        340        350        360
GAKPAAKPQE TSVADEAPEV TATVISYDNY VTILDEETLK AWIAKLEKAP VFAFDTETDS
       370        380        390        400        410        420
LDNISANLVG LSFAIEPGVA AYIPVAHDYL DAPDQISRER ALELLKPLLE DEKALKVGQN
       430        440        450        460        470        480
LKYDRGILAN YGIELRGIAF DTMLESYILN SVAGRHDMDS LAERWLKHKT ITFEEIAGKG
       490        500        510        520        530        540
KNQLTFNQIA LEEAGRYAAE DADVTLQLHL KMWPDLQKHK GPLNVFENIE MPLVPVLSRI
       550        560        570        580        590        600
ERNGVKIDPK VLHNHSEELT LRLAELEKKA HEIAGEEFNL SSTKQLQTIL FEKQGIKPLK
       610        620        630        640        650        660
KTPGGAPSTS EEVLEELALD YPLPKVILEY RGLAKLKSTY TDKLPLMINP KTGRVHTSYH
       670        680        690        700        710        720
QAVTATGRLS STDPNLQNIP VRNEEGRRIR QAFIAPEDYV IVSADYSQIE LRIMAHLSRD
       730        740        750        760        770        780
KGLLTAFAEG KDIHRATAAE VFGLPLETVT SEQRRSAKAI NFGLIYGMSA FGLARQLNIP
       790        800        810        820        830        840
RKEAQKYMDL YFERYPGVLE YMERTRAQAK EQGYVETLDG RRLYLPDIKS SNGARRAAAE
       850        860        870        880        890        900
RAAINAPMQG TAADIIKRAM IAVDAWLQAE QPRVRMIMQV HDELVFEVHK DDVDAVAKQI
       910        920
HQLMENCTRL DVPLLVEVGS GENWDQAH   

Encoded by polA gene


OTHER NAME(S):
ECK3855
JW3835
resA


DESCRIPTION:
Residues 324-928 constitute the Klenow fragment. [More information is available at EcoGene: EG10746]. DNA Polymerase I (Pol I) is a multifunctional enzyme that combines a DNA polymerase activity, a 5' to 3' exonuclease activity and a 3' to 5' proofreading exonuclease activity. [More information is available at EcoCyc: EG10746].


Nucleic acid sequence

        10         20         30         40         50         60
atggttcaga tcccccaaaa tccacttatc cttgtagatg gttcatctta tctttatcgc
        70         80         90        100        110        120
gcatatcacg cgtttccccc gctgactaac agcgcaggcg agccgaccgg tgcgatgtat
       130        140        150        160        170        180
ggtgtcctca acatgctgcg cagtctgatc atgcaatata aaccgacgca tgcagcggtg
       190        200        210        220        230        240
gtctttgacg ccaagggaaa aacctttcgt gatgaactgt ttgaacatta caaatcacat
       250        260        270        280        290        300
cgcccgccaa tgccggacga tctgcgtgca caaatcgaac ccttgcacgc gatggttaaa
       310        320        330        340        350        360
gcgatgggac tgccgctgct ggcggtttct ggcgtagaag cggacgacgt tatcggtact
       370        380        390        400        410        420
ctggcgcgcg aagccgaaaa agccgggcgt ccggtgctga tcagcactgg cgataaagat
       430        440        450        460        470        480
atggcgcagc tggtgacgcc aaatattacg cttatcaata ccatgacgaa taccatcctc
       490        500        510        520        530        540
ggaccggaag aggtggtgaa taagtacggc gtgccgccag aactgatcat cgatttcctg
       550        560        570        580        590        600
gcgctgatgg gtgactcctc tgataacatt cctggcgtac cgggcgtcgg tgaaaaaacc
       610        620        630        640        650        660
gcgcaggcat tgctgcaagg tcttggcgga ctggatacgc tgtatgccga gccagaaaaa
       670        680        690        700        710        720
attgctgggt tgagcttccg tggcgcgaaa acaatggcag cgaagctcga gcaaaacaaa
       730        740        750        760        770        780
gaagttgctt atctctcata ccagctggcg acgattaaaa ccgacgttga actggagctg
       790        800        810        820        830        840
acctgtgaac aactggaagt gcagcaaccg gcagcggaag agttgttggg gctgttcaaa
       850        860        870        880        890        900
aagtatgagt tcaaacgctg gactgctgat gtcgaagcgg gcaaatggtt acaggccaaa
       910        920        930        940        950        960
ggggcaaaac cagccgcgaa gccacaggaa accagtgttg cagacgaagc accagaagtg
       970        980        990       1000       1010       1020
acggcaacgg tgatttctta tgacaactac gtcaccatcc ttgatgaaga aacactgaaa
      1030       1040       1050       1060       1070       1080
gcgtggattg cgaagctgga aaaagcgccg gtatttgcat ttgataccga aaccgacagc
      1090       1100       1110       1120       1130       1140
cttgataaca tctctgctaa cctggtcggg ctttcttttg ctatcgagcc aggcgtagcg
      1150       1160       1170       1180       1190       1200
gcatatattc cggttgctca tgattatctt gatgcgcccg atcaaatctc tcgcgagcgt
      1210       1220       1230       1240       1250       1260
gcactcgagt tgctaaaacc gctgctggaa gatgaaaagg cgctgaaggt cgggcaaaac
      1270       1280       1290       1300       1310       1320
ctgaaatacg atcgcggtat tctggcgaac tacggcattg aactgcgtgg gattgcgttt
      1330       1340       1350       1360       1370       1380
gataccatgc tggagtccta cattctcaat agcgttgccg ggcgtcacga tatggacagc
      1390       1400       1410       1420       1430       1440
ctcgcggaac gttggttgaa gcacaaaacc atcacttttg aagagattgc tggtaaaggc
      1450       1460       1470       1480       1490       1500
aaaaatcaac tgacctttaa ccagattgcc ctcgaagaag ccggacgtta cgccgccgaa
      1510       1520       1530       1540       1550       1560
gatgcagatg tcaccttgca gttgcatctg aaaatgtggc cggatctgca aaaacacaaa
      1570       1580       1590       1600       1610       1620
gggccgttga acgtcttcga gaatatcgaa atgccgctgg tgccggtgct ttcacgcatt
      1630       1640       1650       1660       1670       1680
gaacgtaacg gtgtgaagat cgatccgaaa gtgctgcaca atcattctga agagctcacc
      1690       1700       1710       1720       1730       1740
cttcgtctgg ctgagctgga aaagaaagcg catgaaattg caggtgagga atttaacctt
      1750       1760       1770       1780       1790       1800
tcttccacca agcagttaca aaccattctc tttgaaaaac agggcattaa accgctgaag
      1810       1820       1830       1840       1850       1860
aaaacgccgg gtggcgcgcc gtcaacgtcg gaagaggtac tggaagaact ggcgctggac
      1870       1880       1890       1900       1910       1920
tatccgttgc caaaagtgat tctggagtat cgtggtctgg cgaagctgaa atcgacctac
      1930       1940       1950       1960       1970       1980
accgacaagc tgccgctgat gatcaacccg aaaaccgggc gtgtgcatac ctcttatcac
      1990       2000       2010       2020       2030       2040
caggcagtaa ctgcaacggg acgtttatcg tcaaccgatc ctaacctgca aaacattccg
      2050       2060       2070       2080       2090       2100
gtgcgtaacg aagaaggtcg tcgtatccgc caggcgttta ttgcgccaga ggattatgtg
      2110       2120       2130       2140       2150       2160
attgtctcag cggactactc gcagattgaa ctgcgcatta tggcgcatct ttcgcgtgac
      2170       2180       2190       2200       2210       2220
aaaggcttgc tgaccgcatt cgcggaagga aaagatatcc accgggcaac ggcggcagaa
      2230       2240       2250       2260       2270       2280
gtgtttggtt tgccactgga aaccgtcacc agcgagcaac gccgtagcgc gaaagcgatc
      2290       2300       2310       2320       2330       2340
aactttggtc tgatttatgg catgagtgct ttcggtctgg cgcggcaatt gaacattcca
      2350       2360       2370       2380       2390       2400
cgtaaagaag cgcagaagta catggacctt tacttcgaac gctaccctgg cgtgctggag
      2410       2420       2430       2440       2450       2460
tatatggaac gcacccgtgc tcaggcgaaa gagcagggct acgttgaaac gctggacgga
      2470       2480       2490       2500       2510       2520
cgccgtctgt atctgccgga tatcaaatcc agcaatggtg ctcgtcgtgc agcggctgaa
      2530       2540       2550       2560       2570       2580
cgtgcagcca ttaacgcgcc aatgcaggga accgccgccg acattatcaa acgggcgatg
      2590       2600       2610       2620       2630       2640
attgccgttg atgcgtggtt acaggctgag caaccgcgtg tacgtatgat catgcaggta
      2650       2660       2670       2680       2690       2700
cacgatgaac tggtatttga agttcataaa gatgatgttg atgccgtcgc gaagcagatt
      2710       2720       2730       2740       2750       2760
catcaactga tggaaaactg tacccgtctg gatgtgccgt tgctggtgga agtggggagt
      2770       2780
ggcgaaaact gggatcaggc gcactaa   

Last modification date: Oct. 7, 2011