A free energy landscape screen reveals the disordered conformational ensemble of tropoelastin

Understanding how proteins explore their conformational energy landscapes is essential for linking sequence to function, yet current ensemble methods are limited by sampling inefficiency and poor scalability to large disordered systems. Here we introduce a free energy landscape screen (FELS), a conceptually different approach that replaces sampling-centric ensemble fitting with broad exploration of energy landscapes, screening thousands of landscape shapes--from highly funneled to flat and rugged. By systematically biasing and evaluating large conformer pools according to contact propensities derived from experiment, FELS efficiently identifies sets of conformers that best reproduce experimental data and highlights candidates for structural refinement, without being restricted by chain length or amount of disorder. To demonstrate the power of this approach we applied it to a previously intractable system, human tropoelastin (hTE), a [~]700-residue precursor of elastin. FELS provides the first experimentally defined atomistic view of the hTE conformational ensemble, revealing that this protein is intrinsically disordered yet exhibits distinct local secondary structure and specific, transient medium- and long-range contacts that organize its ensemble. These findings reconcile long-standing conflicting models and demonstrate that FELS provides a general, experimentally driven framework for mapping conformational energy landscapes of large proteins across the continuum between structural order and disorder.