
Type:Protein
SpeciesReactivity:H
B=Bovine;Ca=Cat;Ch=Chicken;D=Dog;EQ=Equine;GP=GuineaPig;H=Human;M=Mouse;P=Porcine;Pr=Primate;R=Rat;Rb=Rabbit;Y=Yeast;Xe=Xenopus;Ze=Zebrafish;;;;NA-NotApplicable;STP=Step-TactinProteins;AllHumanIGFbindingprotein4(IGFBP-4)wasisolatedfromhumanplasmabasedonitsABIlitytobindimmobilizedIGF-I.HumanIGFBP-4CDNAencodesa258aminoacid(aa)residueprecursorproteinwithapredicted21aaresiduesignalpeptidethatisprocessedtogeneratethe237aaresiduematurehumanIGFBP-4.ThehumanIGFBP-4containsapotentialN-linkedglycosylationsiteandsharesapproximately90%aminoacidsequenceidentitywithboththemouseandratIGFBP-4.AccordingtothenomenclatureofIGFBPsdefinedatthe4thInternationalSymposiumofIGFs(1997,Tokyo),sixhigh-affinityIGFbindingproteins(IGFBP-1,-2,-3,-4,-5,-6),andfourIGFBP-relatedproteins(IGFBPr-1,-2,-3,-4)havenowbeenidentified.AllIGFBPshaveahighcysteinecontentandshareconservedcysteineresiduesthatareclusteredintheamino-andcarboxy-terminalthirdsofthemolecule.IGFBPshavebeenshowntoeitherinhibitorenhancetheBIOLOGicalactivitiesofIGF,oractinanIGF-independentmanner.Post-translationalmodificationofIGFBPs,includingphosphorylationandproteolysis,havebeenshowntomodifytheaffinitiesofthebindingproteinsforIGFandmayindirectlyregulateIGFactions(Jones,J.I.andD.R.Clemons,1995,EndocrineRev.16:3;Kelly,K.M.etal.,1996,Intl.J.Biochem.CellBiol.28:619-637;Kim,H-S.etal.,1997,Proc.Natl.Acad.Sci.USA94:12981).