Globular protein

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Globular protein

Globular proteins, or spheroproteins are one of the two main protein

Protein

Proteins are organic compounds made of amino acids arranged in a linear chain and joined together by peptide bonds between the carboxyl and amino groups of adjacent amino acid Residue ....
classes, comprising "globe"

Sphere

A sphere is a symmetrical geometrical object. In non-mathematical usage, the term is used to refer either to a round ball or to its two-dimensional surface....
-like proteins that are more or less soluble in aqueous solutions

Aqueous solution

An aqueous solution is a solution in which the solvent is water. It is usually shown in chemical equations by appending to the relevant formula....
(where they form colloidal solutions). This main characteristic helps distinguishing them from fibrous proteins

Fibrous protein

Scleroproteins are one of the two main classes of protein tertiary structure .They are also called fibrous proteins....
(the other class), which are practically insoluble.

The term globin

Globin

A globin is a hemeprotein that incorporates the globin fold. Globins are used to transport heme....
can refer more specifically to proteins including the globin fold

Globin fold

The globin fold is a common three-dimensional tertiary structure in proteins. This fold typically consists of eight alpha helix, although some proteins have additional helix extensions at their termini....
.

Globular structure and solubility
The term globular protein is quite old (dating probably from the 19th century) and is now somewhat archaic given the hundreds of thousands of proteins and more elegant and descriptive structural motif

Structural motif

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Encyclopedia

Globular proteins, or spheroproteins are one of the two main protein

Protein

Sphere

Aqueous solution

Fibrous protein

Scleroproteins are one of the two main classes of protein tertiary structure .They are also called fibrous proteins....
(the other class), which are practically insoluble.

The term globin

Globin

A globin is a hemeprotein that incorporates the globin fold. Globins are used to transport heme....
can refer more specifically to proteins including the globin fold

Globin fold

Globular structure and solubility

The term globular protein is quite old (dating probably from the 19th century) and is now somewhat archaic given the hundreds of thousands of proteins and more elegant and descriptive structural motif

Structural motif

In an unbranched, polymer biological molecule, such as a protein or a strand of RNA, a structural motif is a three-dimensional structural element or protein folding within the chain, which appears also in a variety of other molecules....
vocabulary. The globular nature of these proteins can be determined without the means of modern techniques, but only by using ultracentrifuge

Ultracentrifuge

The ultracentrifuge is a centrifuge optimized for spinning a rotor at very high speeds, capable of generating acceleration as high as 1,000,000 g ....
s or dynamic light scattering

Scattering

Scattering is a general physical process where some forms of radiation, such as light, sound, or moving particles,are forced to deviate from a straight trajectory by one or more localized non-uniformities in the medium through which they pass....
techniques.

The spherical structure is induced by the protein's tertiary structure

Tertiary structure

In biochemistry and chemistry, the tertiary structure of a protein or any other macromolecule is its three-dimensional structure, as defined by the atomic coordinates....
. The molecule's apolar (hydrophobic) amino acids are bounded towards the molecule's interior whereas polar

Polar

Polar may refer to:As a noun:*Cervecer?a Polar, C.A., Venezuelan brewery and beer*Polar , Norwegian electronic music artist*Polar , satellite launched by NASA in 1996....
(hydrophilic) amino acids are bound outwards, allowing dipole-dipole interactions with the solvent

Solvent

A solvent is a liquid or gas that dissolves a solid, liquid, or gaseous solute, resulting in a solution.The most common solvent in everyday life is water....
, which explains the molecule's solubility.

A wide range of roles in the organism

Unlike fibrous proteins which only play a structural function, globular proteins can act as:

Enzyme
Enzyme

Enzymes are biomolecules that catalysis chemical reactions. Almost all enzymes are proteins. In enzymatic reactions, the molecules at the beginning of the process are called Substrate , and the enzyme converts them into different molecules, the products....
s, by catalyzing
Catalysis

Catalysis is the process in which the reaction rate of a chemical reaction is either increased or decreased by means of a chemical substance known as a catalyst....
organic reactions taking place in the organism
Organism

In biology, an organism is any life thing . In at least some form, all organisms are capable of response to stimulus , reproduction, growth and developmental biology, and maintenance of homeostasis as a stable whole....
in mild conditions and with a great specificity. Different esterase
Esterase

An esterase is a hydrolase enzyme that splits esters into an acid and an alcohol in a chemical reaction with water called hydrolysis.A wide range of different esterases exist that differ in their Substrate specificity, their protein structure, and their biological function....
s fulfill this role.
Messenger
Messenger

A messenger is a person employed in business to convey messages, official dispatches, telegrams, letters, or parcels, and go on special errands as part of their duties....
s, by transmitting messages to regulate biological processes. This function is done by hormone
Hormone

Hormones are chemicals released by cells that affect cells in other parts of the body. Only a small amount of hormone is required to alter cell metabolism....
s, i.e. insulin
Insulin

Insulin is a hormone with extensive effects on both metabolism and several other body systems . Insulin causes most of the body's cells to take up glucose from the blood , storing it as glycogen in the liver and muscle, and stops use of fat as an energy source....
etc.
Transporter
Transporter

Transporter may refer to vehicles or transport:* transporter, a business or person involved in the transport of goods or people* transporter, a vehicle used to transport objects or material, especially a heavy hauler or related type of truck...
s of other molecules through membrane
Cell membrane

The cell membrane is the interface between the cellular machinery inside the cell and the fluid outside.It is a semipermeable lipid bilayer found in all cell ....
s
Stocks of amino acid
Amino acid

In chemistry, an amino acid is a molecule containing both amine and carboxyl functional groups. These molecules are particularly important in biochemistry, where this term refers to alpha-amino acids with the general formula H2NCHRCOOH, where R is an organic substituent....
s.
Regulatory roles are also performed by globular proteins rather than fibrous proteins.

Members

Among the most known globular proteins is Hemoglobin

Hemoglobin

Hemoglobin is the iron-containing oxygen-transport metalloprotein in the red blood cells of vertebrates, and the tissues of some invertebrates....
, a member of the globin protein family. Other globular proteins are the immunoglobulins (IgA, IgD, IgE, IgG and IgM), and alpha

Alpha globulin

Alpha Globulins are a group of globular proteins in blood plasma, which are highly mobile in alkaline or electrically charged solutions. They inhibit certain blood protease and inhibitor activity....
, beta

Beta globulins

Beta globulins are a group of globular proteins in blood plasma thatare more mobile in alkaline or electrically charged solutions than gamma globulins, but less mobile than alpha globulins....
and gamma

Gamma globulin

Gamma globulins, or Ig's, are a class of proteins in the blood, identified by their position after serum protein electrophoresis. The most significant gamma globulins are antibody....
globulins. See protein electrophoresis

Protein electrophoresis

In medicine, protein electrophoresis is a method of analysing a mixture of proteins by means of gel electrophoresis, mainly in blood blood plasma ....
for more information on the different globulins. Nearly all enzymes with major metabolic

Metabolism

Metabolism is the set of chemical reactions that occur in living organisms in order to maintain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments....
functions are globular in shape, as well as many signal transduction

Signal transduction

In biology, 'signal transduction' refers to any process by which a cell converts one kind of signal or stimulus into another. Most processes of signal transduction involve ordered sequences of biochemistry chemical reaction inside the cell, which are carried out by enzymes, activated by Second messenger systems, resulting in a signal tran...
proteins.