Secondary Structure of Bovine _S2-Casein: Theoretical and Experimental Approaches

¹ U. S. Department of Agriculture, Agriculture Research Service Eastern Regional Research Center, 600 E. Mermaid Lane, Wyndmoor, PA 19038

Circular dichroism and Fourier transform infrared spectroscopy of bovine _S2-casein both report a 24 to 32% content of -helix. A consensus of sequence based predictions for -helix suggests a Lys⁷⁷-Gln⁹¹ helix within the sequence (Ser⁶¹-Arg¹²⁵). This motif is repeated at (Ser¹⁴³-Leu²⁰⁷), and this region contains a longer Thr¹⁴⁵-Leu¹⁷⁷ predicted -helix. A short, seven-member -helix may also organize the N-terminal peptide that precedes the first phosphoserine [-Srp-]₃ cluster. As was found for other caseins studied by these spectroscopic methods, a high degree of extended ß-sheet (30%) and turns (25 to 30%) are predicted for _S2-casein.

Key Words: _S2-casein • Fourier Transform infrared • circular dichroism • secondary structure

Submitted on November 6, 2000
Accepted on April 16, 2001

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