Structure of recombinant human parathyroid hormone in solution using multidimensional NMR spectroscopy

Area of Science:

• Biochemistry
• Structural Biology
• Protein NMR Spectroscopy

Background:

• Human parathyroid hormone (hPTH) is a critical regulator of calcium and phosphate homeostasis.
• Understanding the solution structure of hPTH is essential for elucidating its biological function and interactions.
• Recombinant prolyl-hPTH(1-84) was used to study the structured-state of the hormone.

Purpose of the Study:

• To determine the solution structure of human parathyroid hormone (hPTH) using multidimensional NMR spectroscopy.
• To characterize the secondary and tertiary structural elements of hPTH in a structured-favoring environment.
• To analyze the conformational ensemble and flexibility of hPTH in solution.

Main Methods:

• Multidimensional NMR spectroscopy, including 3D 1H DQF-COSY, TOCSY, and NOESY.
• Nuclear Overhauser Effect (NOE) data analysis for structure calculation.
• Restrained molecular dynamics and energy minimization.
• 15N-labeled protein for heteronuclear multiple-quantum coherence (HMQC) experiments.

Main Results:

• Identified three well-defined helices in the N-terminus (residues 3-10, 17-27, 30-37).
• Observed a short, less-defined helix (residues 57-62) and loose turns in the C-terminus.
• The mid-region of hPTH was found to be unstructured.
• Evidence of tertiary structure formation through long-range NOEs.
• Refined structures classified into a stable conformational ensemble, highlighting hormone flexibility.

Conclusions:

• The solution structure of hPTH is characterized by distinct N-terminal helices and a flexible C-terminal region.
• The unstructured mid-region acts as a flexible linker between the terminal domains.
• hPTH exhibits a tendency towards tertiary structure and exists as an ensemble of stable conformations in solution.
• These findings provide insights into the structural dynamics and functional mechanisms of hPTH.