Segmental flexibility of immunoglobulin M molecules

Phylogenesis of the general structure of immunoglobulins. Rigidity of 7 S immunoglobulins and restricted flexibility of the 17 S immunoglobulins of the tortoise, Testudo horsfieldi

“…However, this freedom is much more restricted as compared to IgM of mammals. [ 13 ]. *** Taken from [5].…”

“…The absorption coefficient was assumed to be 14.0 for both proteins. The molar ratio of DNS to protein was estimated as previously described [1,6] and found to vary from 35-45 in 17 S immunoglobulins and from 2.3--4.5 in the 7 S. The lifetime of excited DNS molecules (~-) and degree of fluorescence polarisation (p) were measured as described elsewhere [1]; the rotational correlation time (¢h)* was calculated as previously [1,2,5,6]. …”

“…Previously it has been shown that IgG and IgM of mammals (man, rabbit and rat) are characterized by a flexible structure which facilitates the interaction of the active Fab fragments with antigenic determinants [1][2][3][4][5]. It has also been found that carp macroglobulins have a considerably more compact general structure [6].…”

“…Therefore, it was interesting to elucidate whether the differences in the lability of the general structure of immunoglobulins of mammals and carp are connected with the evolution process or may be accounted for by some other phenomena. The purpose of this study is the investigation of the general structure of the 7 S and 17 S immunoglobulins of the tortoise, a representative of the intermediate vertebrate class of reptiles, by the fluorescence polarisation technique previously used for the investigation of the general structure of IgG and IgM of mammals and carp [1][2][3][4][5][6]. These immunoglobulins were found to have some features similar to those of IgG and IgM of mammals [7].…”