What amino acids are found in globular proteins?
Proteins: Globular and Membrane Globular Proteins:
One feature that most globular proteins share is the ability to bind certain small molecules.
The most common type of globular protein that is capable of binding a small molecule is an enzyme. Enzymes:
CO-FACTORS- Most enzymes require a supplementary chemical group, called a co-factor,to be fully active. There are organic and inorganic co-factors, many enzymes contain both.
Glycoproteins:
Enzymatic Glycosylation
Non-Enzymatic Glycosylation
Membrane Proteins:
>can be categorized as:
Clinical Correlate: Non-Enzymatic Glycosylation
The three main types of structural or fibrous protiens fround in the human body are: collagens, elastins and keratins. Collagen:
Amino Acid Sequence: Glycine at every third position.
Collagen Helix: Only 3.0 residues per turn vs. 3.6 for an average a-helix. Triple Helix: Three collagen helices wound very tightly together. Collagen Fibrils: The triple helices are arranged in staggered fashion (covalent crosslinks vital to the structure of mature collagen). Important specializations seen in collagen: 1) Proline is very abundant and can be hydroxylated by prolyl hydroxylase to form hydroxyproline. Co-factor for prolyl hydroxylase is: ascorbic acid (vitamin C).
2) Lysine is abundant and can be hydroxylated by lysyl hydroxylase to form hydroxylysine. Co-factor for lysyl hydroxylase is: ascorbic acid (vitamin C).
3) Hydroxylysines can be glycosylated on their newly acquired -OH groups. (sugar attachment)
4) Cysteine residues at the ends of the collagen helices are oxidized to form disulfide bridges, this places the chains in proper orientation for triple helix formation.
5) Covalent crosslinks are formed between allysine and lysine during fibril formation:
Collagen Maturation: Nucleus:
ER:
Extracellular:
Elastin: is another important class of insoluble fibrous proteins. Elastin lacks the genetic complexity, diversity and helical structure of collagen. Two features elastin and collagen share:
Unique to elastin:
Keratins: insoluble structural proteins found in skin, nails and hair There are two types of keratins:
In hair and nails the a-helices of adjacent strands are crosslinked by disulfide bridges.
Permanent Wave:
Some heritable diseases related to collagen: Osteogenesis Imperfecta Ehlers-Danlos Syndrome Menkes' Disease Antibodies:
All antibodies belong to the family of proteins called immunoglobulins, named for their role in the immune response, i.e. their ability to specifically recognize antigens (foreign invaders). Antibody Structure: -Immunoglobulins share a common structure of three subunits arranged in a trimeric unit. -Although, some immunoglobulins are more complex and contain multiples of this unit. Features of the Antibody-
IgG Molecule (an illustration of the basic immunoglobulin unit):
"Hinge" region:
Fab ("antigen binding") fragment contains the variable regions -----> binding sites Fc ("crystallizable") fragment mediates many of the functions common to an immunoglobulin class. (Fc portion is derived solely from the heavy chains, differences in the heavy chain constant regions are what distinguish one class of immunoglobulin from another.) Antigen Recognition:
Hypervariable Regions:
Hapten:
Types of Interactions Important in Antigen Binding:
Clinical Correlate: Vaccines
Success: chicken pox More Difficult: HIV, has the ability to alter it's cell surface proteins in endless permutations Clinical Correlate: Autoimmune Diseases
© Dr. Noel Sturm 2021 What type of amino acids are in globular proteins?Globular proteins are folded such that their tertiary structure consists of the polar, or hydrophilic, amino acids arranged on the outside and the nonpolar, or hydrophobic, amino acids on the inside of the three-dimensional shape.
Which amino acid would most likely be found in the internal core of a globular protein?Tyrosine occurs mostly in the core, and thus shows quite hydrophobic properties in a protein environment. Charged amino acids including aspartic acid, glutamic acid, lysine, and arginine, not surprisingly, tend to occur on the surface.
What are globular proteins composed of?At a simple level, a globular protein may be considered to consist of a hydrophobic core surrounded by a hydrophilic external surface which interacts with water. The tertiary fold of the polypeptide is such that those residues with apolar side chains are buried in the centre, while the polar residues remain exposed.
Which amino acid sequence is most likely to be found on the exterior of a globular protein?Polar and/or hydrophilic (“water loving”) amino acids would be found on the exterior of globular proteins near the aqueous environment. Hydrophobicity and hydrophilicity are major forces that drive the formation of the tertiary or three-dimensional shape of a protein post translation.
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