The polyketide natural product Leptomycin B inhibits nuclear export mediated by the karyopherin protein chromosomal region maintenance 1 (CRM1). Here, we present 1.8- to 2.0-Å-resolution crystal structures of CRM1 bound to Leptomycin B and related inhibitors Anguinomycin A and Ratjadone A. Structural and complementary chemical analyses reveal an unexpected mechanism of inhibition involving covalent conjugation and CRM1-mediated hydrolysis of the natural products’ lactone rings. Furthermore, mutagenesis reveals the mechanism of hydrolysis by CRM1. The nuclear export signal (NES)-binding groove of CRM1 is able to drive a chemical reaction in addition to binding protein cargos for transport through the nuclear pore complex.

Retinol plays a vital role in the immune response to infection, yet proteins that mediate retinol transport during infection have not been identified. Serum amyloid A (SAA) proteins are strongly induced in the liver by systemic infection and in the intestine by bacterial colonization, but their exact functions remain unclear. Here we show that mouse and human SAAs are retinol binding proteins. Mouse and human SAAs bound retinol with nanomolar affinity, were associated with retinol in vivo, and limited the bacterial burden in tissues after acute infection. We determined the crystal structure of mouse SAA3 at a resolution of 2 Å, finding that it forms a tetramer with a hydrophobic binding pocket that can accommodate retinol. Our results thus identify SAAs as a family of microbe-inducible retinol binding proteins, reveal a unique protein architecture involved in retinol binding, and suggest how retinol is circulated during infection.

With contributions from the global natural product (NP) research community, and continuing the Raw Data Initiative, this review collects a comprehensive demonstration of the immense scientific value of disseminating raw nuclear magnetic resonance (NMR) data, independently of, and in parallel with, classical publishing outlets.