Bollen Yves J M, Kamphuis Monique B, van Mierlo Carlo P M
Department of Structural Biology, Vrije Universiteit, 1081 HV Amsterdam, The Netherlands.
Proc Natl Acad Sci U S A. 2006 Mar 14;103(11):4095-100. doi: 10.1073/pnas.0509133103. Epub 2006 Mar 6.
Many native proteins occasionally form partially unfolded forms (PUFs), which can be detected by hydrogen/deuterium exchange and NMR spectroscopy. Knowledge about these metastable states is required to better understand the onset of folding-related diseases. So far, not much is known about where PUFs reside within the energy landscape for protein folding. Here, four PUFs of the relatively large apoflavodoxin (179 aa) are identified. Remarkably, at least three of them are partially misfolded conformations. The misfolding involves side-chain contacts as well as the protein backbone. The rates at which the PUFs interconvert with native protein have been determined. Comparison of these rates with stopped-flow data positions the PUFs in apoflavodoxin's complex folding energy landscape. PUF1 and PUF2 are unfolding excursions that start from native apoflavodoxin but do not continue to the unfolded state. PUF3 and PUF4 could be similar excursions, but their rates of formation suggest that they are on a dead-end folding route that starts from unfolded apoflavodoxin and does not continue all of the way to native protein. All PUFs detected thus are off the protein's productive folding route.
许多天然蛋白质偶尔会形成部分未折叠形式（PUFs），可通过氢/氘交换和核磁共振光谱检测到。为了更好地理解折叠相关疾病的发病机制，需要了解这些亚稳态。到目前为止，关于PUFs在蛋白质折叠能量景观中的位置知之甚少。在这里，鉴定出了相对较大的脱辅基黄素氧还蛋白（179个氨基酸）的四种PUFs。值得注意的是，其中至少三种是部分错误折叠的构象。错误折叠涉及侧链接触以及蛋白质主链。已经确定了PUFs与天然蛋白质相互转化的速率。将这些速率与停流数据进行比较，可将PUFs定位在脱辅基黄素氧还蛋白复杂的折叠能量景观中。PUF1和PUF2是从未折叠的脱辅基黄素氧还蛋白开始但不会继续到未折叠状态的展开过程。PUF3和PUF4可能是类似的过程，但它们的形成速率表明它们处于从未折叠的脱辅基黄素氧还蛋白开始且不会一直持续到天然蛋白质的死端折叠途径上。因此检测到的所有PUFs都偏离了蛋白质的有效折叠途径。
