资源环境科技发展态势分析平台

Voltage-gated potassium (K-v) channels coordinate electrical signalling and control cell volume by gating in response to membrane depolarization or hyperpolarization. However, although voltage-sensing domains transduce transmembrane electric field changes by a common mechanism involving the outward or inward translocation of gating charges(1-3), the general determinants of channel gating polarity remain poorly understood(4). Here we suggest a molecular mechanism for electromechanical coupling and gating polarity in non-domain-swapped K-v channels on the basis of the cryo-electron microscopy structure of KAT1, the hyperpolarization-activated K-v channel from Arabidopsis thaliana. KAT1 displays a depolarized voltage sensor, which interacts with a closed pore domain directly via two interfaces and indirectly via an intercalated phospholipid. Functional evaluation of KAT1 structure-guided mutants at the sensor-pore interfaces suggests a mechanism in which direct interaction between the sensor and the C-linker hairpin in the adjacent pore subunit is the primary determinant of gating polarity. We suggest that an inward motion of the S4 sensor helix of approximately 5-7 angstrom can underlie a direct-coupling mechanism, driving a conformational reorientation of the C-linker and ultimately opening the activation gate formed by the S6 intracellular bundle. This direct-coupling mechanism contrasts with allosteric mechanisms proposed for hyperpolarization-activated cyclic nucleotide-gated channels(5), and may represent an unexpected link between depolarization- and hyperpolarization-activated channels.

The cryo-electron microscopy structure of the hyperpolarization-activated K+ channel KAT1 points to a direct-coupling mechanism between S4 movement and the reorientation of the C-linker.

Environmental change is rapidly accelerating, and many species will need to adapt to survive(1). Ensuring that protected areas cover populations across a broad range of environmental conditions could safeguard the processes that lead to such adaptations(1-3). However, international conservation policies have largely neglected these considerations when setting targets for the expansion of protected areas(4). Here we show that-of 19,937 vertebrate species globally(5-8)-the representation of environmental conditions across their habitats in protected areas (hereafter, niche representation) is inadequate for 4,836 (93.1%) amphibian, 8,653 (89.5%) bird and 4,608 (90.9%) terrestrial mammal species. Expanding existing protected areas to cover these gaps would encompass 33.8% of the total land surface-exceeding the current target of 17% that has been adopted by governments. Priority locations for expanding the system of protected areas to improve niche representation occur in global biodiversity hotspots(9), including Colombia, Papua New Guinea, South Africa and southwest China, as well as across most of the major land masses of the Earth. Conversely, we also show that planning for the expansion of protected areas without explicitly considering environmental conditions would marginally reduce the land area required to 30.7%, but that this would lead to inadequate niche representation for 7,798 (39.1%) species. As the governments of the world prepare to renegotiate global conservation targets, policymakers have the opportunity to help to maintain the adaptive potential of species by considering niche representation within protected areas(1,2).

Protected areas would need to expand to 33.8% of the total land surface to adequately represent environmental conditions across the habitats of amphibians, birds and terrestrial mammals, far exceeding the current 17% target.