High and low molecular weight kininogen and plasma prekallikrein/plasma kallikrein in villous capillaries of human term placenta

After limited digestion of purified human HMW-kininogen by plasmin, the kininogen molecule consists of two disulfide-linked chains in which the bradykinin sequence resides in the "light chain" portion. Kinin was released from this molecule by plasma kallikrein at a two- to three-fold more rapid rate than from uncleaved HMW-kininogen. Similarly, when normal human plasma or prekallikrein deficient plasma was treated with sufficient streptokinase to activate plasminogen the subsequent rate of release of kinin by kallikrein was enhanced. The digestion of HMW-kininogen by plasmin as well as kinin relea^s was inhibited by epsilon aminocaproic acid at a concentration of 10−3 M, suggesting that one or more lysine residues was critical to the plasmin-HMW-kininogen interaction. Leukocyte elastase cleaved HMW-kininogen into low molecular weight fragments without releasing kinin but plasma kallikrein could then release kinin from a low molecular weight component of elastase-digested HMW-kininogen (≦50 kd mol. wt.). Elastase destroyed the coagulant properties of the kininogenWhen HMW-kininogen was converted to two-chain, disuifide-linked molecules, either by plasmin or kallikrein, the quantity of antigen detected in an ELISA with polyclonal antibody to human light chain antigens was significantly increased. Expression of antigen detectable with a monoclonal antibody to an epitope located close to the disulfide interchange in the light chain was not increased by prior limited digestion with these enzymesIt is possible that minimal activation of plasminogen in vivo may facilitate kinin release by kallikrein. In addition, in quantifying antigenic properties of HMW-kininogen in plasma, care should be taken to block in vitro activation of plasminogen or prekallikrein. Since leukocyte elastase can be released during clotting of whole blood, it might then serve as a regulator of coagulation through its inactivation of coagulant properties of HMW-kininogen

Download Full-text

Plasma High-Molecular-Weight and Low-Molecular-Weight Kininogens: Their Structures and Physiological Functions

10.1055/s-0039-1682648 ◽

1977 ◽

Author(s):

S. Iwanaga ◽

H. Kato ◽

Y.-N. Han ◽

N. Hashimoto ◽

T. Sugo ◽

...

Keyword(s):

Molecular Weight ◽

Coagulation Factor ◽

Disulfide Bridge ◽

Light Chains ◽

Low Molecular Weight ◽

Plasma Kallikrein ◽

Amino Acid Residues ◽

Rich Region ◽

Bovine Plasma ◽

Structural Differences

Bovine plasma contains two kininogens. One of them, HMW kininogen, has recently been characterized as a new coagulation factor, which is required for the activation of Hageman factor-mediated pathway. To elucidate the structural differences between HMW and LMW kininogens, these were fragmented with plasma kallikrein and snake venom kininogenase, and the resulting products were chemically identified. The kallikrein simultaneously released bradykinin and fragment 1·2 from HMW kininogen. Fragment 1·2 was a histidine-rich glycopeptide consisting of 110 amino acid residues, and its whole sequence and the location of the sugar moieties were established. The venom kininogenase liberated only bradykinin from LMW kininogen. Kinin (and fragment 1·2)-free proteins consisted of heavy and light chains. These chains constituted, respectively, the NH2-and COOH-terminal portions of both parent molecules and were held by a single disulfide bridge. The detailed studies on these chains indicated that the NH2-terminal portions of HMW and LMW kininogens are very similar for each other, whereas their COOH-terminal portions differ significantly. Concerning the results that HMW kininogen overcomes impaired coagulation and fibrinolysis of the kininogen deficient plasmas, and the kinin-free HMW protein has a weak corrective activity, it seems that the histidine-rich region found only in HMW kininogen may be closely related to the functions of the kininogen.

Download Full-text

A high-performance oil-free backing pump for electron microscopes

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100107691 ◽

1978 ◽

Vol 36 (1) ◽

pp. 110-111

Author(s):

G.K.W. Balkau ◽

E. Bez ◽

J.L. Farrant

Keyword(s):

Molecular Weight ◽

Electron Microscope ◽

Hot Spots ◽

High Performance ◽

Carbonaceous Material ◽

Contamination Rate ◽

Low Molecular Weight ◽

Principal Source ◽

Rotary Pumps ◽

Electron Microscopes

The earliest account of the contamination of electron microscope specimens by the deposition of carbonaceous material during electron irradiation was published in 1947 by Watson who was then working in Canada. It was soon established that this carbonaceous material is formed from organic vapours, and it is now recognized that the principal source is the oil-sealed rotary pumps which provide the backing vacuum. It has been shown that the organic vapours consist of low molecular weight fragments of oil molecules which have been degraded at hot spots produced by friction between the vanes and the surfaces on which they slide. As satisfactory oil-free pumps are unavailable, it is standard electron microscope practice to reduce the partial pressure of organic vapours in the microscope in the vicinity of the specimen by using liquid-nitrogen cooled anti-contamination devices. Traps of this type are sufficient to reduce the contamination rate to about 0.1 Å per min, which is tolerable for many investigations.

Download Full-text