Coupled spatial variations in precipitation and long-term erosion rates across the Washington Cascades

Past studies of tectonically active mountain ranges have suggested strong coupling and feedbacks between climate, tectonics and topography. For example, rock uplift generates topographic relief, thereby enhancing precipitation, which focuses erosion and in turn influences rates and spatial patterns of further rock uplift. Although theoretical links between climate, erosion and uplift have received much attention, few studies have shown convincing correlations between observable indices of these processes on mountain-range scales. Here we show that strongly varying long-term (>10(6)-10(7) yr) erosion rates inferred from apatite (U-Th)/He cooling ages across the Cascades mountains of Washington state closely track modern mean annual precipitation rates. Erosion and precipitation rates vary over an order of magnitude across the range with maxima of 0.33 mm yr(-1) and 3.5 m yr(-1), respectively, with both maxima located 50 km west (windward) of the topographic crest of the range. These data demonstrate a strong coupling between precipitation and long-term erosion rates on the mountain-range scale. If the range is currently in topographic steady state, rock uplift on the west flank is three to ten times faster than elsewhere in the range, possibly in response to climatically focused erosion.     

Structural basis for selective recognition of ESCRT-III by the AAA ATPase Vps4

The AAA+ ATPases are essential for various activities such as membrane trafficking, organelle biogenesis, DNA replication, intracellular locomotion, cytoskeletal remodelling, protein folding and proteolysis. The AAA ATPase Vps4, which is central to endosomal traffic to lysosomes, retroviral budding and cytokinesis, dissociates ESCRT complexes (the endosomal sorting complexes required for transport) from membranes. Here we show that, of the six ESCRT--related subunits in yeast, only Vps2 and Did2 bind the MIT (microtubule interacting and transport) domain of Vps4, and that the carboxy-terminal 30 residues of the subunits are both necessary and sufficient for interaction. We determined the crystal structure of the Vps2 C terminus in a complex with the Vps4 MIT domain, explaining the basis for selective ESCRT-III recognition. MIT helices alpha2 and alpha3 recognize a (D/E)xxLxxRLxxL(K/R) motif, and mutations within this motif cause sorting defects in yeast. Our crystal structure of the amino-terminal domain of an archaeal AAA ATPase of unknown function shows that it is closely related to the MIT domain of Vps4. The archaeal ATPase interacts with an archaeal ESCRT-III-like protein even though these organisms have no endomembrane system, suggesting that the Vps4/ESCRT-III partnership is a relic of a function that pre-dates the divergence of eukaryotes and Archaea.