Final answer:
Collagen is the most abundant ECM protein, making up 25% of the total protein in mammals, providing structural support to various tissues, and is not water-soluble due to its specific amino acid composition and molecular structure.
Step-by-step explanation:
The most abundant extracellular matrix (ECM) protein is collagen. Collagen has the remarkable distinction of constituting about 25% of the total protein mass in mammals. It is vital for providing structural support to various tissues such as the skin, bones, tendons, blood vessels, and many others. Collagen fibers are capable of forming a strong and flexible network, which is essential for maintaining the structure and integrity of connective tissues.
The general physical properties of collagen indicate that it is a protein with a unique composition of amino acids, providing it with particular structural qualities. The three most common amino acids in collagen are glycine, proline, and hydroxyproline. Given collagen's structural role and its interaction with various other ECM components such as proteoglycans, it is not generally soluble in water. Its physical properties are a consequence of its molecular structure, which includes a triple helix formation contributing to its strength and insolubility.