HYPK: A marginally disordered protein sensitive to charge decoration

• 成果类型: Article
• 署名作者: Firouzbakht, Arash; Haider, Austin; Gaalswyk, Kari; Alaeen, Sepehr; Ghosh, Kingshuk; Gruebele, Martin
• 署名单位: University of Illinois System; University of Illinois Urbana-Champaign; University of Denver; University of Denver; University of Illinois System; University of Illinois Urbana-Champaign; University of Illinois System; University of Illinois Urbana-Champaign; University of Illinois System; University of Illinois Urbana-Champaign; University of Illinois System; University of Illinois Urbana-Champaign
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-9120
• DOI: 10.1073/pnas.2316408121
• 发表日期: 2024-04-30
• 关键词: single-molecule spectroscopy; temperature-induced collapse; simulations; dimensions; consensus; BEHAVIOR

摘要

Intrinsically disordered proteins (IDPs) that lie close to the empirical boundary separating IDPs and folded proteins in Uversky's charge-hydropathy plot may behave as marginal IDPs and sensitively switch conformation upon changes in environment (temperature, crowding, and charge screening), sequence, or both. In our search for such a marginal IDP, we selected Huntingtin - interacting protein K (HYPK) near that boundary as a candidate; PKI alpha , also near that boundary, has lower secondary structure propensity; and Crk1, just across the boundary on the folded side, has higher secondary structure propensity. We used a qualitative F & ouml;rster resonance energy transfer - based assay together with circular dichroism to simultaneously probe global and local conformation. HYPK shows several unique features indicating marginality: a cooperative transition in end - to - end distance with temperature, like Crk1 and folded proteins, but unlike PKI alpha ; enhanced secondary structure upon crowding, in contrast to Crk1 and PKI alpha ; and a cross - over from salt - induced expansion to compaction at high temperature, likely due to a structure - to - disorder transition not seen in Crk1 and PKI alpha . We then tested HYPK's sensitivity to charge patterning by designing charge - flipped variants including two specific sequences with identical amino acid composition that markedly differ in their predicted size and response to salt. The experimentally observed trends, also including mutants of PKI alpha , verify the predictions from sequence charge decoration metrics. Marginal proteins like HYPK show features of both folded and disordered proteins that make them sensitive to physicochemical perturbations and structural control by charge patterning.