AsianScientist (Apr. 7, 2015) – Researchers have found that membrane fusion proteins known as SNAREs disassemble in a single explosive burst, contradicting the existing theory which held that the complex unwinds in a processive manner. These results have been published in Science.
SNARE proteins such as N-ethylmaleimide-sensitive factor (NSF), alpha-soluble NSF attachment protein (α-SNAP) and soluble SNAP receptors (SNAREs) are the minimal machinery required for membrane fusion. To induce membrane fusion, the proteins combine to form a SNARE complex in a four helical bundle, subsequently disassembling for reuse.
NSF can bind to the energy source molecule, adenosine triphosphate (ATP). In the ATP-bound form, NSF develops internal tension via cleavage of ATP. This process is used to exert great force on SNARE complexes, eventually pulling them apart. However, although about 30 years have passed since SNAREs were discovered, how NSF/α-SNAP disassembled the SNARE complex has remained a mystery.
In the present study, a research team led by Professors Yoon Tae-Young of the Department of Physics at the Korea Advanced Institute of Science and Technology (KAIST) and Reinhard Jahn of the Max-Planck-Institute for Biophysical Chemistry, used various single-molecule biophysical methods that allowed them to monitor and manipulate individual protein complexes.
“We have learned that NSF releases energy in a burst within 20 milliseconds to ‘tear’ the SNARE complex apart in a one-step global unfolding reaction, which is immediately followed by the release of SNARE proteins,” said Yoon.
Previously, it was believed that NSF disassembled a SNARE complex by unwinding it in a processive manner. Also, largely unexplained was how many cycles of ATP hydrolysis were required and how these cycles were connected to the disassembly of the SNARE complex.
Yoon added, “From our research, we found that NSF requires hydrolysis of ATPs that were already bound before it attached to the SNAREs—which means that only one round of an ATP turnover is sufficient for SNARE complex disassembly. Moreover, this is possible because NSF pulls a SNARE complex apart by building up the energy from individual ATPs and releasing it at once, yielding a ‘spring-loaded’ mechanism.”
NSF is a member of a family of ATP-cleaving enzymes which is essential for many cellular functions such as DNA replication and protein degradation, microtubule severing, signal transduction and the regulation of gene expression.
The article can be found at: Ryu et al. (2015) Spring-Loaded Unraveling Of A Single SNARE Complex By NSF In One Round Of ATP Turnover.
———
Source: KAIST.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.
