HA-detected experiments for the backbone assignment of intrinsically disordered proteins

Area of Science:

• Biochemistry
• Structural Biology
• Spectroscopy

Background:

• Natively unfolded proteins present challenges for standard NMR assignment due to chemical exchange.
• Proline-rich sequences further complicate assignment protocols.
• Accurate sequential assignment is crucial for understanding protein function.

Purpose of the Study:

• To develop a novel alpha proton detection strategy for sequential assignment of natively unfolded proteins.
• To overcome limitations of existing methods regarding pH sensitivity and proline content.
• To provide a more streamlined and unambiguous NMR assignment approach.

Main Methods:

• Utilized alpha proton (HA) detection for NMR experiments.
• Employed intraresidual and sequential correlation experiments involving (15)N, (13)C', and H(alpha) nuclei.
• Leveraged the reduced residue-type dependence of (15)N and (13)C' chemical shifts.
• Tested the protocol on GB1 and the proline-rich EspF(U) protein.

Main Results:

• The HA-detection method is insensitive to chemical exchange, enabling assignment at any pH.
• Straightforward assignment of proline-rich polypeptides was achieved without specialized experiments.
• Assignment was streamlined using solely intraresidual and sequential correlation experiments.
• Achieved 90% assignment of (1)H(alpha), (13)C(alpha), (13)C', and (15)N chemical shifts in EspF(U).

Conclusions:

• The proposed HA-detection based strategy is highly effective for natively unfolded proteins.
• This method is particularly advantageous for assigning proline-rich protein sequences.
• The approach offers a robust and efficient tool for structural biologists studying disordered proteins.