生物谷：研究人員確定了一個對丙肝病毒DNA復制至關重要的酶的機制。這個名為NS3的酶是新的乙肝治療法的靶標,，它的作用是打開DNA和RNA使其得以復制,。Sua Myong和同事用單分子光譜學方法觀察了NS3沿乙肝病毒DNA雙螺旋的“蠕動”。這個酶每步打開3個DNA堿基對(堿基對是DNA雙股上對應的由氫鍵連接的核苷酸),。但是，在堿基對打開之前,，還有隱藏的步驟,。這個酶先是一、二大步,，然后一個小步爬上堿基對,，直到張力足夠大從而導致解卷和3個堿基對看起來是同時的開鏈。
英文原文鏈接：
http://www.sciencedaily.com/releases/2007/07/070726142007.htm
Using single-molecule fluorescence analysis, Institute for Genomic Biology professor Sua Myong and physics professor Taekjip Ha led a team that discovered the mechanism by which the hepatitis C helicase unwinds DNA and RNA for replication. Ha is also affiliated with the Institute for Genomic Biology and the Howard Hughes Medical Center. (Credit: L. Brian Stauffer, U. of I. News Bureau)
原始出處:
Science 27 July 2007:
Vol. 317. no. 5837, pp. 513 - 516
DOI: 10.1126/science.1144130
Spring-Loaded Mechanism of DNA Unwinding by Hepatitis C Virus NS3 Helicase
Sua Myong,1,2* Michael M. Bruno,3,4 Anna M. Pyle,3,4 Taekjip Ha1,2,4
NS3, an essential helicase for replication of hepatitis C virus, is a model enzyme for investigating helicase function. Using single-molecule fluorescence analysis, we showed that NS3 unwinds DNA in discrete steps of about three base pairs (bp). Dwell time analysis indicated that about three hidden steps are required before a 3-bp step is taken. Taking into account the available structural data, we propose a spring-loaded mechanism in which several steps of one nucleotide per adenosine triphosphate molecule accumulate tension on the protein-DNA complex, which is relieved periodically via a burst of 3-bp unwinding. NS3 appears to shelter the displaced strand during unwinding, and, upon encountering a barrier or after unwinding >18 bp, it snaps or slips backward rapidly and repeats unwinding many times in succession. Such repetitive unwinding behavior over a short stretch of duplex may help to keep secondary structures resolved during viral genome replication.
1 Physics Department, University of Illinois, 1110 West Green Street, Urbana, IL 61801, USA.
2 Institute for Genomic Biology, University of Illinois, 1206 West Gregory Drive, Urbana, IL 61801, USA.
3 Molecular Biophysics and Biochemistry, Yale University, 266 Whitney Avenue, Room 334A, Bass Building, New Haven, CT 06511, USA.
4 Howard Hughes Medical Institute.
* To whom correspondence should be addressed. E-mail: [email protected]
