Title: Crystal Structure of the Nephila clavipes Major Ampullate Spidroin 1A N-terminal Domain Reveals Plasticity at the Dimer Interface

Abstract

Spider dragline silk is a natural polymer harboring unique physical and biochemical properties that make it an ideal biomaterial. Artificial silk production requires an understanding of the in vivo mechanisms spiders use to convert soluble proteins, called spidroins, into insoluble fibers. Controlled dimerization of the spidroin N-terminal domain (NTD) is crucial to this process. In this paper, we report the crystal structure of the Nephila clavipes major ampullate spidroin NTD dimer. Comparison of our N. clavipes NTD structure with previously determined Euprosthenops australis NTD structures reveals subtle conformational alterations that lead to differences in how the subunits are arranged at the dimer interface. We observe a subset of contacts that are specific to each ortholog, as well as a substantial increase in asymmetry in the interactions observed at the N. clavipes NTD dimer interface. These asymmetric interactions include novel intermolecular salt bridges that provide new insights into the mechanism of NTD dimerization. We also observe a unique intramolecular “handshake” interaction between two conserved acidic residues that our data suggest adds an additional layer of complexity to the pH-sensitive relay mechanism for NTD dimerization. The results of a panel of tryptophan fluorescence dimerization assays probing the importance of these interactions supportmore » our structural observations. Based on our findings, we propose that conformational selectivity and plasticity at the NTD dimer interface play a role in the pH-dependent transition of the NTD from monomer to stably associated dimer as the spidroin progresses through the silk extrusion duct.« less

Authors:

Atkison, James H. ^[1]; Parnham, Stuart ^[1]; Marcotte, Jr., William R. ^[2]; Olsen, Shaun K. ^[1]

---

+ Show Author Affiliations

1. Medical Univ. of South Carolina, Charleston, SC (United States)
2. Clemson Univ., SC (United States)

Publication Date:

Thu Jul 21 00:00:00 EDT 2016

Research Org.:

Argonne National Laboratory (ANL), Argonne, IL (United States). Advanced Photon Source (APS)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES); National Institute of General Medical Sciences (NIGMS); National Institutes of Health (NIH); Office of Research Infrastructure Programs (ORIP)

OSTI Identifier:

1328789

Grant/Contract Number:  

W-31-109-ENG-38; P41 GM103403; S10 RR029205; AC02-06CH11357; S10 RR027139-01

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Biological Chemistry

Additional Journal Information:

Journal Volume: 291; Journal Issue: 36; Journal ID: ISSN 0021-9258

Publisher:

American Society for Biochemistry and Molecular Biology

Country of Publication:

United States

Language:

ENGLISH

Subject:

59 BASIC BIOLOGICAL SCIENCES; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; crystal structure; dimerization; protein self-assembly; protein structure; structural biology; structure-function; x-ray crystallography; MaSp1A; spidroin; spider silk; structural plasticity; Nephila clavipes