Primary Information
BoMiProt ID	Bomi5
Protein Name	Complement C4
Organism	Bos taurus
Uniprot ID	P01030
Milk Fraction	Whey
Aminoacid Length	920
Molecular Weight	101885
FASTA Sequence	Download
Gene Name	C4
Protein Existence Status	Reviewed: Experimental evidence at protein level
Secondary Information
Protein Function	most heterogeneous protein of the complement system; act as opsonizing molecules; C4b2a complex (the CP C3 convertase) remains on the activator and mediates downstream activation by cleaving C3 into C3b and C3a; C4b may offer a nucleophile for the cleavage of the thioester in nascent C3b
Biochemical Properties	C4A is more prone to attach to amine groups of an activator, whereas C4B reacts preferentially with hydroxyl groups;
Significance in milk	recruit inflammatory leucocytes to the sites of an inflammation and activate their effector mechanisms
PTMs	Glycosylated: 4 N linked glycosylation site; α and ß-chains are glycosylated, but no accurate assessment of carbohydrate content in the γ-chain has been reported; C4 in human plasma contains mannose, galactose, glucosamine and sialic acid; contain complex biantennary glycans with varying degrees of sialylation; Human C4A recovered from cerebrospinal fluid was identified to contain an O-linked core 1 glycan; sulfation of three tyrosine residues
Site(s) of PTM(s) N-glycosylation, O-glycosylation, Phosphorylation
Predicted Disorder Regions	NA
DisProt Annotation
TM Helix Prediction	1TMH; (73-95)
Additional Comments	Carbohydrate incorporation can be blocked by tunicamycin; underglycosylated pro-C4 protein is more rapidly catabolized than the corresponding fully glycosylated protein; underglycosylated native C4, produced in the presence of tunicamycin, had approximately the same specific biological activity as glycosylated C4