combinationproteinMolecular division ofamino acidIn addition to the components, there are also non amino acid substances, which are calledCofactorThe two are combined in covalent or non covalent form, and are often separated from biomaterials as a whole.Simple proteinIt refers to that there is no non protein component in the molecular composition except the polypeptide protein component composed of amino acids, which is called pure protein.Many proteins in nature belong to this class.The binding protein is composed of simple protein and other compounds, and the other compounds that are combined are usually called the non protein part (auxiliary group) of the binding protein.It is divided intoNucleoprotein(containing nucleic acid)glycoprotein(containing polysaccharide)Lipoprotein(containing lipids), phosphoprotein (containing phosphoric acid)Metalloprotein(including metal) andChromoprotein(including pigment), etc.
In addition to amino acid components, the molecules of binding proteins also contain non amino acid substances, which are called cofactors. The two are bound in covalent or non covalent forms and are often separated from biological materials as a whole.Simple proteinIt refers to that there is no non protein component in the molecular composition except the polypeptide protein component composed of amino acids, which is called pure protein.Many proteins in nature belong to this class.The binding protein is composed of simple protein and other compounds, and the other compounds that are combined are usually called the non protein part (auxiliary group) of the binding protein.It can be divided into nucleoprotein (containing nucleic acid), glycoprotein (containing polysaccharide), lipoprotein (containing lipid), phosphoprotein (containing phosphoric acid), metalloprotein (containing metal) and chromoprotein (containing pigment) according to different non protein parts.[1]
classification
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Binding proteins are mainly divided into the following categories.Chromoprotein: Protein combines with pigment substances, such ashemoglobin。Lecithin: The combination of protein and lecithin, as in bloodfibrin、Vitellin。Lipoprotein: soluble in water, it is the combination of fat and protein. Lipoprotein is a tool for the body to transport fat in the body.includeChyle microparticle、Very low density lipoprotein, low-density lipoproteinHigh density lipoprotein。Metalloproteins: proteins bind to metals, such as transferrin and copper zinc binding proteins. Many enzymes contain metal ions.Mucin or glycoprotein: containscarbohydrateProteins such as mannose and galactose,Human cellsThe mucus secreted by the tissue contains mucin.Nucleoprotein: Protein combines with nucleic acid. Nucleoprotein exists in tissue germ and human gland tissue.[2]
Glycoprotein
The sugar content of protein covalently bound with sugar is less than 4%.There are disaccharides, oligosaccharides and polysaccharides.Glycoproteins are a very complex class of proteins with a wide variety, such as:Blood group glycoprotein, hormone glycoprotein, cell membrane glycoproteinovalbuminas well asExogenous agglutinin。
Mucoproteins
The sugar content of protein combined with aminopolysaccharide is less than 4%.It usually containsβoneaminoglucose, combined with one or more of the following sugars: galactose, mannose, rhamnoseGlucuronic acidEtc.
Nucleoprotein
A protein that binds to nucleic acids.Such as: DNA nucleoprotein, ribosome, simple plant virus, etc.Nuclear protein exists in all living organisms, and both cytoplasm and nucleus contain nuclear protein.
Lipoprotein
A binding protein consisting of protein and fat or lipids.Lipoproteins are widely found in animals. Lipoproteins in the blood of higher animals includeαMonolipoproteins andβA lipoprotein.Lipoprotein in cell membrane affects the permeability of cell membrane.
Phosphoproteins
A protein that covalently binds to phosphoric acid.Phosphoric acid is bound to the side chain hydroxyl of serine or threonine of protein, and has dissociative acid groups, which mainly exist in egg yolk and milk.Such as caseinPepsin(pepsin)。[2]
Metalloproteins
A protein that binds directly to metal ions.For example, ferritin contains Fe2+, nitrogenase containing Mo2+And Fe2+, carboxypeptidase containing Zn2+，Superoxide dismutaseContaining Cu2+And Zn2+Many proteins contain a small amount of metals.
Heme Proteins
A protein that binds to the heme of the cofactor. Its main function is to participate in respiration or oxygen transport.Such as hemoglobin of higher animals, hemocyanin of lower animals, and chlorophyllin,catalase, myoglobin, etc.
Flavoproteins
A protein that binds to flavin nucleotide FAD or FMN.For example:Xanthoredoxin, D-amino acid oxidase, etc.[3]
Important binding proteins
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hemoglobin
Hemoglobin is a chromoprotein mainly existing in the red blood cells of vertebrates. Its main function is to carry oxygen andcarbon dioxide。100 ml whole blood of normal human body contains 12-16 g hemoglobin.The iron content of human hemoglobin is about 0.33%~0.34%, and its relative molecular weight is about 67000.Hemoglobin is composed of globin and cofactor heme.Its composition varies with different sources, and the difference is only in the globin part.
hemoglobinThe globin in is composed of four peptide chainsFour level structureProtein.Each of the four peptide chains can bind to one heme, and each heme can bind to one oxygen molecule, so oneHemoglobin moleculeIt can bind 4 oxygen molecules, and this kind of protein is calledOxyhemoglobin。Oxyhemoglobin is very unstable, and its binding force to oxygen often changes with the level of oxygen partial pressure. Hemoglobin transports oxygen through such oxygenation reaction.
The globin in hemoglobin in normal adults is composed of two identical a-peptide chains and two identical peptide chainstwoβtwoThe symbol is called hemoglobin A, which is represented by HbA.The adult body contains 96% HbA and 0.5%~4% HbAtwo，HbAtwoThe composition of is atwoβtwo。The hemoglobin of the fetus is mainly HbF, and its composition is atwoγtwo。a、β、γandδPeptideAmino acid residueThe order of has been determined by determination, whereαA peptide chain is composed of 141 residues,β、γandδThe peptide chain consists of 146 residues.Their primary structures are different, but their secondary and tertiary structures are very similar.[4]
Nucleoprotein
Nucleoprotein is called nucleoprotein because it was first found in the nucleus. It is a binding protein in cells.Nuclear proteins are found in both the nucleus and cytoplasm.In addition, nucleoproteins are also found in viruses, chromosomes and ribosomes.Nucleoprotein plays a unique role in the growth and reproduction of organisms.
Nucleoprotein is composed of cationicBasic protein(e.g. histones andProtamine）And protein cofactor (nucleic acid).Histone containsBasic amino acid(such as lysine and arginine), so it is alkaline.hisrelative molecular mass11 000~21 000.Protamine exists in some protamine nucleoproteins and is alkaline because it is rich in arginine.[1]
