Leucine， isoleucine， and valine are three essential branched-chain amino acids (BCAA) account for 40-45% of total essential amino acids. BCAA stimulates protein synthesis primarily in skeletal muscles， and it can directly transport to circulatory blood stream bypassing the liver. Hence， a protein enriched with BCAA is an important therapeutic target for the dietary treatment of chronic liver disease. The present study is to design a synthetic protein enriched with BCAA and the challenge is to maximize the BCAA content， keeping the balanced ratio of leucine， isoleucine， valine - 2: 1: 1.2 as specified by WHO/UNU/FAO. Here， we turned the general concept of homology modeling and tried to find a sui... More
Leucine， isoleucine， and valine are three essential branched-chain amino acids (BCAA) account for 40-45% of total essential amino acids. BCAA stimulates protein synthesis primarily in skeletal muscles， and it can directly transport to circulatory blood stream bypassing the liver. Hence， a protein enriched with BCAA is an important therapeutic target for the dietary treatment of chronic liver disease. The present study is to design a synthetic protein enriched with BCAA and the challenge is to maximize the BCAA content， keeping the balanced ratio of leucine， isoleucine， valine - 2: 1: 1.2 as specified by WHO/UNU/FAO. Here， we turned the general concept of homology modeling and tried to find a suitable scaffold (α-helix) to host an excess amount of BCAA for increased stability and digestibility. A total of 50 protein models were constructed by using SWISS-MODEL， Modeller 9.17， ProtParam tool， and allergen online tools. Out of 50 different protein models， protein model-50 was found to be best， which had a well-defined 3D structure， good in silico digestibility， balanced ratio of BCAA and showed 65.57% structure identity to the template apo-bovine α-lactalbumin (1F6R). Templates search was performed against PDB using PSI-BLAST， SWISS-MODEL， PROFUNC， I-TASSER， and ConSurf. The secondary structure was predicted by PSSPred， PSIPRED， I-TASSER， PORTER， and SPIDER2. The modeled structure of protein Model-50 was validated by PROCHECK， ERRAT， ProSA， and QMEAN. COACH and ProFUNC tools were performed to determine the functional effects of protein model-50. Overall， the BCAA was enriched from 22 to 56.4% with the balanced ratio of Leu: Ile: Val (2: 1: 1.2). The Ramachandran plot showed 97.7% of the amino acid residues in allowed regions with ERRAT score of 86.05. We have successfully modeled the complete three-dimensional structure of the target protein model-50 using highly reputed computational tools.
