Holoproteins
As we saw when the tertiary structure of proteins was discussed, holoproteins can be classified into two groups:
Biology 2nd Baccalaureate
4.4.3.1. Holoproteins
Fibrous or filamentous proteins or scleroproteins
They have a filamentous conformation (tertiary structure), are resistant and insoluble in water and appear mainly in animals. They generally perform structural functions. Collagen, keratin, elastin, actin, myosin, and fibroins belong to this group.
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In connective, cartilaginous, and bone tissues. |
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Rich in cysteine. In epidermal formations, such as hair, nails, wool, horns, hooves, feathers, etc. |
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Elastin |
It has elasticity. In blood vessels, lungs, etc. |
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Fibroin |
In the silk threads. |
Globular proteins or spheroproteins
They have globular conformation (tertiary and quaternary structure, and are soluble in water or in polar solutions. Protamines, histones, prolamines, glutenins, albumins and globulins belong to this group.
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Very basic |
Soluble in water. They are associated with DNA in the sperm of all animals. |
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Basics |
Soluble in water. They are associated with the DNA of the nucleus (except in sperm) forming chromatin. |
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Soluble in water. They collaborate in the transport of other molecules and act as a reserve of amino acids. Serum albumin from blood plasma, ovalbumin from egg white, lactalbumin from milk, and globin, which is part of hemoglobin, belong to this group. |
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Soluble in saline solutions. Examples are egg ooglobulin, milk lactoglobulin, and blood serum globulins; also α-globulin, which is associated with hemoglobin, and γ-globulins or immunoglobulins, which constitute antibodies. |
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