The characterization of DNA-binding protein from Streptococcus intermediusand elucidate its virulence mechanism

组蛋白样蛋白（HLP）在DNA复制、重组、修复、Mu转座和基因转录调控中发挥作用。除了它们在细胞过程中的作用之外，HLP被认为是一些细菌如化脓性链球菌的粘附素。在本研究中，我们克隆了一个基因编码组蛋白样蛋白（HLPSi）从中间链球菌UNS 46。HLPSi的氨基酸序列与S.化脓性链球菌A374、枯草芽孢杆菌、大肠杆菌HU-1、大肠杆菌HU-2和麻风分枝杆菌TN。HLPSi富含丙氨酸（20.9%）、赖氨酸（13.2%）和精氨酸（4.4%），缺乏色氨酸、酪氨酸、组氨酸和半胱氨酸。利用pGEX表达系统在大肠杆菌JM 109中表达重组蛋白。将推导的HLPSi蛋白氨基酸序列与数据库中已知的蛋白序列进行比较，发现该蛋白与化脓性链球菌A374、枯草芽孢杆菌、大肠杆菌HU-1和HU-2、M. leprae TN。抗HLPSi抗体与S.中间链球菌NCDO 2227、化脓链球菌A374、咽峡炎链球菌TW 1751。星座沙门氏菌NCD 02226、犬牙沙门氏菌Ingbritt、远缘沙门氏菌0 MZ 65、血沙门氏菌ATCC 10556、沙门氏菌ATCC 10556。sanguinis ST 6、S.gordonii查利斯、S.salivarius HT 9 R、S. salivarius NCTC 8168、缓症链球菌ATCC 15913、S. salivarius NCTC 8168、S.mitis ATCC 15913、S. salivarius NCTC 8168、S. salivarius ATCC 15913、S. salivarius NCTC 8168、S. salivarius ATCC 15913。aureus Smith、S. aureus SMF-4。尽管HLPSI的输出机制仍不清楚，但这可能是由于在诱导的膜通透性改变期间蛋白质的释放，导致该蛋白质沿着其它细胞质蛋白质的释放。需要进一步的实验来确定HLPSi与宿主细胞结合功能的各个方面。

The histone-like proteins (HLPs) play a role in DNA replication, recombination, repair, Mutransposition, and regulation of gene transcription. In addition to their roles in cellular processes, HLPs are considered as an adhesin of some bacteria such as Streptococcus pyogenes. In the present study we cloned a gene encoding a histone-l ike protein (HLPSi) from Streptococcus intermediusUNS46. The deduced amino acid sequence of HLPSi showed 90.1%, 71.6%, 62.5%, 60.7%, and 36.4% identity with a histone-like protein of S. pyogenes A374, Bacillus subtilis, Escherichis coli HU-1, E.coli HU-2, and Mycobacterium leprae TN, respectively. HLPSi was rich in alanine (20.9%), lysine (13.2%), and arginine (4.4%) and devoid of tryptophan, tyrosine, histidine, and cysteine. The recombinant protein was expressed in E.coli JM109 by use of the pGEX expression system. Comparison of the deduced amino acid sequence of HLPSi with known protein sequences deposited in databases revealed that this protein had 90.1%, 71.6%, 62.5%, 60.7% and 36.4% identity over 91 aa residues with histone-like DNA-binding proteins of S.pyogenes A374, Bacillus subtilis, E.coli HU-1 and HU-2, and M. leprae TN, respectively. Anti HLPSi antibody reacted the whole cells of S. intermedius NCDO2227, S.pyogenesA374, S anginosus TW1751. S.constellatus NCD02226, S.inutans lngbritt, S.sobrinus 0MZ65, S.sanguinis ATCC10556, S. sanguinis ST6, S.gordonii Challis, S.salivarius HT9R, S. salivarius NCTC8168, S.mitis ATCC15913, S. aureus Smith, S. aureus SMF-4. Although the export mechanism of HLPSI is still unknown, this is perhaps due to the release of the protein during induced alterations in membrane permeability, leading to the release of this protein along with other cytoplasmic proteins. Further experiments are necessary to define the various aspects of the binding function of HLPSi to host cells.