Lysozyme is consisted of 4 disulfide bridges while the number of disulfide bridges for BSA is 17. Nevertheless, lysozyme is known to be a more rigid protein. What are the other factors affecting the rigidity of proteins?
Does amount of a specific secondary structure like alpha-helix or beta-sheet necessarily determine the rigidity of a protein?
Lysozyme is much smaller (Structure 1HEN 129 amino acids) than serum albumin (structure 1AO6 585 amino acids). Lysozyme can be considered a single domain, while serum albumin consists of several subdomains (see Fig.1 inArticle Molecular Dynamics Simulation and Free Energy Studies on the...
).Flexibility is part of the function of serum albumin, it serves as carrier for many different hydrophobic compounds, that do not utilize one define binding site, but intercalate in many different sites into the hydrophobic core of the molecule. While secondary structure (hydrogen bonds) and disulfide bonds certainly have an effect on flexibility, core packing also has a major effect. If you look at the localization of the disulfide bonds within albumin, you will see that they are quite local in the individual subdomains, keeping the helices of the subdomain together, but allowing the different subdomains to move relatively to each other.
Lysozyme is much smaller (Structure 1HEN 129 amino acids) than serum albumin (structure 1AO6 585 amino acids). Lysozyme can be considered a single domain, while serum albumin consists of several subdomains (see Fig.1 inArticle Molecular Dynamics Simulation and Free Energy Studies on the...
).Flexibility is part of the function of serum albumin, it serves as carrier for many different hydrophobic compounds, that do not utilize one define binding site, but intercalate in many different sites into the hydrophobic core of the molecule. While secondary structure (hydrogen bonds) and disulfide bonds certainly have an effect on flexibility, core packing also has a major effect. If you look at the localization of the disulfide bonds within albumin, you will see that they are quite local in the individual subdomains, keeping the helices of the subdomain together, but allowing the different subdomains to move relatively to each other.
Indeed there is a difference in modular architecture between the enzymes in your example. To provide a general answer to your second question; More alpha-helices (as seen in trans-membrane proteins for example) or B-barrels are definitely more "rigid" compared to proteins that consist of many loops but with a high amount of disulfide bridges. Generally, but not exclusively, a high amount of disulfide bridges occur in thermostable enzymes or enzymes adapted to harsh environments.
Following what Annemarie Honegger and Michiel Vanmeert said, the important points are: 1) the density of disulfide bonds (disulfide bonds per residue), 2) the percentage of structured residues, 3) the topology of the molecule (spatial disposition and connection of the secondary structure motifs) and, very importantly, 4) the location of the disulfide bonds within that topology.
Lysozyme and albumin have been regarded as a hard protein and a soft protein, respectively, regarding adsorption onto surfaces, the first one adsorbing with minor conformational changes, and the second one adsorbing with substantial conformational changes.
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