The oligosaccharide chains of cobra venom factor are required for complement activation

Protective effect of cobra venom factor on pulmonary injury induced by oleic acid

The protective effect of cobra venom factor (CVF), separated from the venom of Naja naja atra, on pulmonary injury induced by oleic acid was reported. The blood gas tensions, tidal volume, transthoracic pressure and pulmonary arterial pressure in anaesthetized dogs were continually monitored. The experimental results showed that CVF, given 20 h before the dosage depleting complements exceed 95%, significantly attenuated oleic acid-induced pulmonary dysfunction, including hypoxemia, increasing veno-arterial shunt and P(A-a)O2 and decreasing dynamic compliance and pulmonary blood flow. Histological examination of lung tissues after the experiment also showed improvement of hyaline membrane formation, alveolar haemorrhage and pulmonary arteriolar thrombosis. It was evident that the depletion of serum complements by CVF inhibited the development of lung injury induced by oleic acid. CVF might be a potentially useful drug for the treatment of respiratory distress syndrome in the near future.

Purification from Vipera lebetina (desert adder) venom of a protein that depletes human complement

A rapid and efficient procedure for purification from Vipera lebetina venom of a low molecular weight anticomplement protein is described. The procedure used gel filtration on Superose 12, followed by ion-exchange chromatography on a Mono Q column. The purified protein migrated on SDS-PAGE as a single band of about 25,000 Da under nonreducing conditions and as a band of 16,000 Da under reducing conditions. Its isoelectric point was estimated to be 7.6 +/- 0.1. The isolated Vipera lebetina protein was found to decrease the hemolytic activity in human serum measured by assays for classical pathway and alternative pathway activation. The loss of the complement activity could be ascribed, at least in part, to a proteolytic cleavage of the alpha chains of C3 and C4. This protein was also found to be without action on human blood coagulation and on purified fibrinogen and Factor B.

Absence of asparagine-linked oligosaccharides from glycoprotein D of herpes simplex virus type 1 results in a structurally altered but biologically active protein

Glycoprotein D (gD) of herpes simplex virus contains three utilized sites (Asn-X-Ser/Thr) for addition of asparagine-linked carbohydrates (N-CHO). Previously, we used oligonucleotide-directed mutagenesis to alter serine or threonine residues to alanine at each N-CHO addition site. Studies with monoclonal antibodies showed that a mutant protein lacking all three sites (now designated AAA) was structurally altered because of the amino acid change at residue 96 as well as the absence of the N-CHO. In this study, we constructed additional single mutations at site 1 (residues 94 and 96) and found that in most cases, the amino acid change itself adversely affected the conformation of gD. However, changing asparagine 94 to glutamine (Q) at site 1 had the least effect on gD. We constructed a second triple mutant, QAA, which lacked all three N-CHO signals. The antigenic conformation of QAA was similar to that of gD produced in the presence of tunicamycin (TM-gD). However, binding of MAbs to the AAA protein or to single mutants altered at site 1 was reduced compared with TM-gD. Wild-type gD and QAA proteins were equally susceptible to digestion by trypsin or Staphylococcus aureus V8 protease. In contrast, the AAA protein was more sensitive to trypsin but less sensitive to V8, again suggesting conformational alterations of the AAA protein. Despite what appeared to be large changes in structure, each mutant complemented the infectivity of a virus lacking gD (F-gD beta). We conclude that the N-CHO and amino acids at N-CHO site 1 play an important role in forming and/or maintaining gD structure, but none of the N-CHO are required for gD to function in the complementation assay.