K‐edge anomalous SAXS for protein solution structure modeling. Issue 2 (24th January 2022) - Virk, Karman
Abstract : In a pilot study, K ‐edge anomalous SAXS signal was obtained from a small dimeric protein containing polyhistidine tags bound to cupric ions, which can be used for the assessment of protein structural models in solution. Abstract : K ‐edge anomalous SAXS intensity was measured from a small, dimeric, partly unstructured protein segment of myosin X by using cupric ions bound to its C‐terminal polyhistidine tags. Energy‐dependent anomalous SAXS can provide key location‐specific information about metal‐labeled protein structures in solution that cannot be obtained from routine SAXS analysis. However, anomalous SAXS is seldom used for protein research due to practical difficulties, such as a lack of generic multivalent metal‐binding tags and the challenges of measuring weak anomalous signal at the metal absorption edge. This pilot feasibility study suggests that weak K ‐edge anomalous SAXS signal can be obtained from transition metals bound to terminally located histidine tags of small proteins. The measured anomalous signal can provide information about the distribution of all metal–protein distances in the complex. Such an anomalous SAXS signal can assist in the modeling and validation of structured or unstructured proteins in solution and may potentially become a new addition to the repertoire of techniques in integrative structural biology.