Integrity of polypeptide chains of spectrin from human erythrocytes

Molar absorptivity and A1%1 cm values for proteins at selected wavelengths of the ultraviolet and visible regions--XVIII

A table of molar absorptivity and A1cm1% values for more than 180 proteins is given. The conditions used to obtain these values and references to the original literature are also'given.

Quantitative analysis of the amino-terminal residues of spectrin by use of the transamination reaction

The metal ion-catalysed transamination reaction has been examined as a means of quantitative amino-terminal analysis of proteins. Application of this method to the erythrocyte membrane protein, spectrin, showed that this protein contained a single amino-terminal residue per 240,000 daltons. This value supports the hypothesis that spectrin is comprised of two polypeptide chains of approx. 220,000 and 250,000 daltons, respectively.

The similarity of the two high-molecular-weight polypeptides of erythrocyte spectrin

1. The two major polypeptides (P1 and P2) of erythrocyte-membrane spectrin were isolated by preparative polyacrylamide-gel electrophoresis. 2. The two polypeptides were shown to possess similar amino acid compositions, both with the characteristically high glutamate and leucine contents of the parent spectrin. 3. The tryptic-peptide 'maps' of the two polypeptides were prepared by a combination of t.l.c. and electrophoresis. 4. Radioactive peptides were prepared by [14C]carboxymethylation and chloramine-T-catalysed [125I]iodination. 5. 'Maps' of both sets of peptides demonstrate a marked similarity between the two polypeptides. 6. These new data confirm earlier evidence for the similarity of the two chains. 7. The number of peptides in the 'maps' of carboxymethylated peptides suggest that polypeptides P1 and P2 are not aggregates.

Physical-chemical studies of spectrin

In recent years considerable progress has been made in the understanding of the structure and function of the red blood cell membrane. The protein spectrin, of high molecular weight and propensity for self-association, appears to play a major role, in concert with actin, in maintaining the shape and integrity of the membrane. A study of the physical-chemical properties of spectrin, and its size, shape, self-association pattern, and its interaction with other components, leads to a plausible model for the way this protein performs its biological role. The evidence from the structure and interactions of spectrin suggests a structure which is relatively symmetrical yet highly expanded, and which allows extensive, two-dimensional network formation with actin. In these respects, the structure of spectrin is quite different from that of myosin, to which it has often been likened.