Product Description

Complement factor B (fB) is purified from normal human serum.Complement factor B is a glycosylated protein composed of a single 93,000 Da polypeptide chain.It is an essential component of the alternative pathway of complement activation and is found in plasma at approximately 200 µg/mL.In the presence of Mg⁺⁺ factor B binds to C3b and the C3b,B complex can be activated by factor D, a serine protease that circulates as an active trypsin-like serine protease.Cleavage of factor B by factor D causes the release of the Ba fragment (33,000 Da) and leaves the 60,000 Bb fragment bound to C3b.This Bb subunit is a serine protease.C3b,Bb is called a C3 and a C5 convertase because it converts both of these proteins to their active forms by cleaving off the small peptides C3a and C5a, respectively (Morikis, D. and Lambris, J.D. (2005); Morley, B.J. and Walport, M.J. (2000)).

Another role for factor B is in the initiation of the alternative pathway. Continuous conversion of native C3 to a C3b-like form is a result of spontaneous hydrolysis of the thioester in C3.This C3(H₂O) binds factor B in a Mg++ stabilized complex.Factor B in the C3(H₂O),B complex can be activated by factor D releasing Ba. During alternative pathway initiation, fluid phase C3(H₂O),Bb cleaves C3 producing metastable C3b which can attach to carbohydrates on cell surfaces and on plasma proteins.If this C3b attaches to a host cell or protein it is rapidly inactivated by a variety of mechanisms due to the actions of factor H, CR1, MCP, and factor I.C3b that attaches to a foreign target lacking these regulators remains active long enough to bind factor B and form C3b,Bb as described above.This is the cell surface-bound C3/C5 convertase of the alternative pathway of complement.C3b,Bb is an unstable trypsin-like serine protease with a half-life of approximately 90 seconds in the absence of factors that accelerate decay (factor H, DAF, and CR1).The proteolytic site is in the C-terminal domain of the Bb subunit (Morley, B.J. and Walport, M.J. (2000)).

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Complement Technology的GVB o是一种基本缓冲液，可用于制备用于补体测定的其他传统缓冲液。可以将Ca ++和Mg ++添加到GVB o中，以制成用于经典途径和凝集素途径测定的GVB ++。可以将MgEGTA添加到GVB o中以进行替代途径测定。EDTA可被添加到GVB Ò准备GVBE抑制补体活化。GVB ø也用于血清和其它测定组分的稀释在许多补体测定中特别是在旁路途径测定（摩根，BP（2000;多兹，AW和Sim，RB（1997））。