Fig. 1.

(A) Schematic and nomenclature of FLN5 RNC (FLN5 + $x$) and truncation (FLN5$\mathrm{\Delta }y$) constructs; $x$ and $y$ represent the FLN6 + secM linker length (measured from the PTC), and the extent of truncation, respectively. (B) Topology and crystal structure of FLN5 (1qfh) colored and labeled to indicate the truncated constructs used in this study. The cis proline P742 is highlighted in yellow (stick representation). (C) ${}^1\text{H}$,${}^{15}\text{N}$-selective optimized flip-angle short transient heteronuclear multiple quantum coherence (SOFAST-HMQC) spectra of FLN5 truncation variants (298 K, 600 MHz). (D) Comparison of ${}^1\text{H}$,${}^{13}\text{C}$-HMQC spectra of FL and $\mathrm{\Delta }$8 with spectra of [${}^{13}\text{CH}_3$-Ile,${}^2\text{H}$]-labeled FLN5 + $L$ RNCs (5) (gray; 298 K, 700 MHz). (E) Comparison of ${}^1\text{H}$,${}^{15}\text{N}$-HSQC spectra of FLN5$\mathrm{\Delta }$6 and FLN5$\mathrm{\Delta }$8, showing a magnified view of representative residues (283 K, 700 MHz). FLN5$\mathrm{\Delta }$6 resonance assignments are not shown where overlapping with FLN5$\mathrm{\Delta }$8 assignments. (F) Comparison of ${}^1\text{H}$,${}^{15}\text{N}$-HSQC spectra of FLN5$\mathrm{\Delta }$6 and FLN5$\mathrm{\Delta }$6(P742A) (283 K, 700 MHz). (G) Comparison of ${}^1\text{H}$,${}^{15}\text{N}$-HSQC spectra of FLN5$\mathrm{\Delta }$4 and FLN5$\mathrm{\Delta }$4(P742A) (283 K, 700 MHz).