The 3-dimensional structure of Glucagon, an alpha helix

Glucagon is a polypeptide hormone consisting of a row of 29 amino acids.

Primary level of protein structure: The sequence of these amino acids is as follows (using 3-letter codes for amino acids):

N-terminal His-Ser-Gln-Gly-Thr-Phe-Thr-Ser-Asp-Tyr-Ser-Lys-Tyr-Leu-Asp-Ser-Arg-Arg-Ala-Gln-Asp-Phe-Val-Gln-Trp-Leu-Met-Asn-Thr C-terminal.

Secondary level of protein structure: This polypeptide chain folds to form a short alpha helix, stabilised by various interactions between the components.

Tertiary level of protein structure: The 3-dimensional structure of the polypeptide chain is locked in place by other stronger bonds between the sidechains ( -R groups) of the amino acid residues.

This shows the glucagon molecule - 29 amino acids - which have orientated themselves into a helix, so that >NH groups (blue+white) are in line with >C=O groups (grey+red) - try the 'Show H bonds' option opposite.
It now shows hydrogen atoms, and double bonds in >C=O in peptide bonds and glutamic acid as well as aromatic sidechains.

The glucagon molecule

Primary structure

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Secondary structure

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Tertiary structure

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