Price S B, Straley S C
Department of Microbiology and Immunology, Chandler Medical Center, University of Kentucky, Lexington 40536.
Infect Immun. 1989 May;57(5):1491-8. doi: 10.1128/iai.57.5.1491-1498.1989.
We are investigating the functions of the three proteins encoded by the V operon (lcrGVH) of the low-calcium response virulence plasmid pCD1 of Yersinia pestis KIM5. The purpose of this study was to define the role of the 18-kilodalton protein encoded by lcrH, the third gene of the V operon. Using marker exchange mutagenesis, we constructed a Y. pestis mutant that failed to express the LcrH protein. This LcrH- mutant was "ATP blind" in that it failed to show altered growth and V-antigen expression at 37 degrees C when 18 mM ATP was present. It also showed only a partial response to 2.5 mM Ca2+. The parental Y. pestis strain showed full growth yield at 37 degrees C and depressed expression of V antigen and of yop (yersinial pCD1-encoded outer membrane protein) genes in response to ATP or Ca2+. In contrast, the LcrH- mutant failed to grow at 37 degrees C in the presence of ATP and showed only limited growth when Ca2+ was present. V-antigen expression in the mutant was not depressed by ATP and only partially depressed by Ca2+. These findings show that LcrH is necessary for the normal response of Y. pestis to ATP and that LcrH contributes to Ca2+ responsiveness. The mutant also showed abnormal yopJ expression, indicating that LcrH also is necessary for normal yop regulation. The LcrH- mutant was avirulent in mice, probably because of its compromised growth at 37 degrees C. These findings indicate that the responses of Y. pestis to ATP and Ca2+ are distinct and that lcrH encodes a protein that is an important mediator of Ca2+ and ATP regulation of pCD1-encoded virulence determinant(s) in Y. pestis.
我们正在研究鼠疫耶尔森氏菌KIM5的低钙反应毒力质粒pCD1的V操纵子（lcrGVH）所编码的三种蛋白质的功能。本研究的目的是确定V操纵子的第三个基因lcrH所编码的18千道尔顿蛋白质的作用。利用标记交换诱变技术，我们构建了一株无法表达LcrH蛋白的鼠疫耶尔森氏菌突变体。该LcrH突变体是“ATP盲性的”，即在存在18 mM ATP的情况下，它在37℃时未能表现出生长变化和V抗原表达的改变。它对2.5 mM Ca2+也仅表现出部分反应。亲本鼠疫耶尔森氏菌菌株在37℃时生长产量完全正常，并且在ATP或Ca2+存在时，V抗原以及yop（鼠疫耶尔森氏菌pCD1编码的外膜蛋白）基因的表达受到抑制。相比之下，LcrH突变体在ATP存在的情况下于37℃无法生长，而在Ca2+存在时仅表现出有限的生长。该突变体中的V抗原表达不受ATP抑制，仅部分受Ca2+抑制。这些发现表明，LcrH对于鼠疫耶尔森氏菌对ATP的正常反应是必需的，并且LcrH有助于对Ca2+作出反应。该突变体还表现出yopJ表达异常，表明LcrH对于正常的yop调控也是必需的。LcrH突变体在小鼠中无致病性，可能是因为其在37℃时生长受损。这些发现表明，鼠疫耶尔森氏菌对ATP和Ca2+的反应是不同的，并且lcrH编码一种蛋白质，该蛋白质是鼠疫耶尔森氏菌中pCD1编码的毒力决定因素的Ca2+和ATP调节的重要介导因子。
