Kothe M, Eroglu B, Mazza H, Samudera H, Powers-Lee S
Department of Biology, Northeastern University, Boston, MA 02115, USA.
Proc Natl Acad Sci U S A. 1997 Nov 11;94(23):12348-53. doi: 10.1073/pnas.94.23.12348.
Carbamoyl-phosphate synthetases (CPSs) utilize two molecules of ATP at two internally duplicated domains, B and C. Domains B and C have recently been shown to be structurally [Thoden, J. B., Holden, H. M., Wesenberg, G., Raushel, F. M. & Rayment, I. (1997) Biochemistry 36, 6305-6316] and functionally [Guy, H. I. & Evans, D. R. (1996) J. Biol. Chem. 271, 13762-13769] equivalent. We have carried out a site-directed mutagenic analysis that is consistent with ATP binding to a palmate motif rather than to a Walker A/B motif in domains B and C. To accommodate our present findings, as well as the other recent findings of structural and functional equivalence, we are proposing a novel mechanism for CPS. In this mechanism utilization of ATP bound to domain C is coupled to carbamoyl-phosphate synthesis at domain B via a nucleotide switch, with the energy of ATP hydrolysis at domain C allowing domain B to cycle between two alternative conformations.
氨甲酰磷酸合成酶（CPSs）在两个内部重复的结构域B和C中利用两分子ATP。最近的研究表明，结构域B和C在结构上[托登，J.B.，霍尔登，H.M.，韦森伯格，G.，劳舍尔，F.M.和雷门特，I.（1997年）《生物化学》36，6305 - 6316]和功能上[盖伊，H.I.和埃文斯，D.R.（1996年）《生物化学杂志》271，13762 - 13769]是等同的。我们进行了定点诱变分析，结果表明ATP与结构域B和C中的掌状基序而非沃克A/B基序结合。为了与我们目前的研究结果以及其他最近关于结构和功能等同性的研究结果相契合，我们提出了一种新的CPS作用机制。在这种机制中，与结构域C结合的ATP的利用通过核苷酸开关与结构域B处的氨甲酰磷酸合成相偶联，结构域C处ATP水解的能量使结构域B在两种交替构象之间循环。
