Versalovic J, Lupski J R
Institute for Molecular Genetics, Baylor College of Medicine, Houston, TX 77030.
Gene. 1993 Dec 22;136(1-2):281-6. doi: 10.1016/0378-1119(93)90480-q.
The dnaG gene encodes primase which synthesizes the primer RNA essential for Escherichia coli chromosomal DNA replication. The nucleotide sequence was determined for the Haemophilus influenzae dnaG gene and used in the molecular evolutionary analysis of primases from six bacterial species. The predicted amino acid (aa) sequence of H. influenzae DnaG contains 593 residues and shares 56% identity with E. coli DnaG. The N-terminal 60% of six aligned bacterial primases contains all 71 absolutely conserved aa residues and several conserved motifs. All six bacterial primases which were sequenced contained a conserved CPFHXEKTPSF(T/S/A)VXXXKQX(F/Y)HCFGC zinc finger (zf) in the N terminus. A basic region in the N-terminal half of the primases contains a conserved motif, G(R/K)X(V/I/L)X(F/Y) (G/S/A)(G/S/A)RX(V/I/L)XXXXP, termed 'RNAP-basic', which is shared only with RNA polymerase (RNAP) large subunits. This conserved sequence represents the first motif common and specific to primases and RNAP subunits. The consensus sequence, PKYLNSPET, lies adjacent to this basic region in bacterial primases and may represent a signature sequence for bacterial DnaG. The C-terminal regions of these primases do not appear to share primary sequence similarities. These findings support our hypothesis that the primase active site of DnaG is located in the N-terminal 60% of the enzyme.
dnaG基因编码引发酶，该酶可合成大肠杆菌染色体DNA复制所必需的引物RNA。测定了流感嗜血杆菌dnaG基因的核苷酸序列，并将其用于六种细菌物种引发酶的分子进化分析。流感嗜血杆菌DnaG的预测氨基酸（aa）序列包含593个残基，与大肠杆菌DnaG的序列一致性为56%。六种比对的细菌引发酶的N端60%包含所有71个绝对保守的aa残基和几个保守基序。所有已测序的六种细菌引发酶在N端都含有一个保守的CPFHXEKTPSF(T/S/A)VXXXKQX(F/Y)HCFGC锌指（zf）。引发酶N端一半的一个碱性区域包含一个保守基序G(R/K)X(V/I/L)X(F/Y)(G/S/A)(G/S/A)RX(V/I/L)XXXXP，称为“RNAP-碱性”，仅与RNA聚合酶（RNAP）大亚基共有。这个保守序列代表了引发酶和RNAP亚基共有的第一个特定基序。共有序列PKYLNSPET在细菌引发酶中与这个碱性区域相邻，可能代表细菌DnaG的一个特征序列。这些引发酶的C端区域似乎没有共享一级序列相似性。这些发现支持了我们的假设，即DnaG的引发酶活性位点位于该酶的N端60%。
