Collagen lathyritic

A better understanding of the structure of collagen IV molecules explains some previous observations. The occurrence of the 7 S domain and nonhelical interruptions in the molecule can explain in part the heterogeneous mixture of collagenous components isolated from basement membrane, particularly when pepsin or other proteases are used to solubilize the protein. The molecules isolated from lathyritic basement membrane by acid extraction are truncated and lack the 7 S domain presumably due to cleavage by endogenous proteases. 

It is clear that these relatively simple organic molecules can prevent the intermolecular cross-linking of collagen. The increased solubility in neutral salt solution as well as in acid buffers indicates that intramolecular cross-linking may also be prevented. This has been confirmed by studies of the a- and /3-components of lathyritic collagen. 

Nikkari and Kulonen (1962) noted that acid-soluble lathyritic collagen exhibited an elevated a/jS ratio only when a prior NaCl extraction was omitted. Lathyrism, therefore, only causes an increased amount of salt-soluble collagen and does not affect any acid-soluble collagen that may already be present. 

Very recently, Martin et al. (1963) found a much slower incorporation of C -glycine into the /3-components prepared from lathyritic collagen compared with normal collagen, as well as the lesser amounts of the /3-com-ponent found in the former case. They could detect no differences in the amino acid compositions of corresponding subunits isolated from lathyritic and normal collagens. 

Nikkari and Kulonen (1962) tried to relate the impaired stability of lathyritic collagen to the hydroxylamine-sensitive linkages. They found values of 0.5-1.5 moles/10 gm for both lathyritic and normal collagen, but in view of the threefold range quoted and the lack of analytical data it is difficult to assess the value of this work. These values are close to those determined by Bello (1960) and later Bello and Bello (1963). The latter authors also noted a fall of molecular weight to 32,000 during the reaction,... 

J4. Jasin, H. E., and Ziff, M., Relationship between soluble collagen and urinary hydroxyproline in the lathyritic rat. Proc. Soc. ExpU. Biol. Med. 110, 837-841 (1962). 

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