Structural studies on lens proteins

1971

The amino acid sequences around the cysteine residues in the lens protein, gamma-crystallin, were studied. Fraction II of the gamma-crystallin from calf lens (Björk, 1964) was used. The protein was oxidized with performic acid and then hydrolysed with trypsin. Six peptides containing cysteic acid were isolated. One of the peptides contained three residues of cysteic acid and the others contained one residue of cysteic acid. We conclude that there are eight unique residues of cysteic acid in the oxidized protein. Amino acid analysis suggests that there are also eight residues of cysteic acid in the molecule, which thus contains only one polypeptide chain.

mentioning

confidence: 93%

Structural studies on bovine γ-crystallin

Croft

1971

“…The sequence of the first 11 residues in the A chain had been determined (Corran & Waley, 1969), and this sequenee includes one methionine and one tryptophan residue. Limited sequences around the cysteine residue have also been reported (Waley, 1965;Mok & Waley, 1967); we now report an extended sequence of 28 residues around this residue. This sequence includes the second residue of methionine in the chain.…”

mentioning

confidence: 50%

“…1), and this was confirmed by cleavage with cyanogen bromide. Of the other chymotryptic peptides in Table 2, peptide Cl was impure, but was derived from the N-terminal region, and peptide C4 from the C-terminal region; peptide C2 was the tetrapeptide isolated by Mok & Waley (1967). Another point, namely the order at the junction of residues 11-12, was confirmed by cleavage in acid.…”

Section: Amino Acidmentioning

confidence: 97%

“…MATERIALS AND METHODS oc-Crystallin. Decapsulated calf lenses were extracted with water and the a-crystallin precipitated at pH5.1 as described by Mok & Waley (1967). The precipitate was dissolved in buffer (40 mM-NaHCO3, M-NaCl, 0.1 m-EDTA, pH8, 0.02% in sodium azide), dialysed against this buffer, and the solution then made 5% (w/v) in sucrose and layered on to a column (44 cm high x 7cm diam.)…”

mentioning

confidence: 99%

See 1 more Smart Citation

Amino acid sequences around the cysteine residue of calf lens α-crystallin

Corran

1971

1. Calf lens alpha-crystallin was carboxymethylated with radioactive sodium iodoacetate to label the thiol group. 2. The protein was then digested with trypsin or alternatively fractionated in urea to obtain the acidic (A) chains, which were then digested with trypsin. Either procedure gave two radioactive peptides containing carboxymethylcysteine. 3. These two peptides were closely related: the longer form contained 28 amino acid residues, and the shorter lacked two residues at the N-terminal end of the longer form. 4. The amino acid sequence of the peptides have been determined. 5. No evidence for the presence of more than one cysteine residue/chain was found. 6. The question of the molecular weight of the chains is discussed.

“…ox-Crystallin. This was prepared from ox lenses as previously described (Mok & Waley, 1967). When the protein was to be for the preparation of A and B chaiiis, calf lenses were used, and the precipitation by (NH4)2S04 was omitted, and instead the protein was purified by chromatography on Sephadex G-200 (Schoenmakers et al 1968).…”

Section: Methodsmentioning

confidence: 99%

N-Terminal sequences of α-crystallin

Corran

1969

The amino acid sequences at the N-terminal ends of the chains of the lens protein, alpha-crystallin, were studied. Both the main kinds of chain in bovine alpha-crystallin (A chains and B chains) have an N-terminal methionine residue, and the amino group is acetylated. Selective purification of the peptides in a tryptic digest of bovine alpha-crystallin gave a preparation consisting largely of the N-terminal peptide from the A chains, and the sequence of this peptide was elucidated. Subsequently, the N-terminal peptides were prepared from separated A and B chains. The proposed sequences are: A chain, acetyl-Met-Asp-Ile-Ala-Ile-Gln-His-Pro-Trp-Phe-Lys; B chain, acetyl-Met-Asp-Ile-Ala-Ile-His-(Pro,Trp)-Ile-Arg. The similarity between the sequences supports the hypothesis that the A and B chains are derived evolutionarily from a common precursor.