Analysis of taste-modifying mechanism of miraculin using miraculin-like proteins

2018 Fiscal Year Final Research Report

• Project/Area Number: 15K07445
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Food science
• Research Institution: Nigata University of Phermacy and Applied Life Sciences
• Principal Investigator: SHIMIZU-IBUKA Akiko 新潟薬科大学, 応用生命科学部, 教授 (60301420)
• Project Period (FY): 2015-04-01 – 2019-03-31
• Keywords: 甘味タンパク質 / 味覚修飾活性 / ミラクリン

Outline of Final Research Achievements

Miracullin-like protein from Vitis vinifera (vvMLP) is a protein which is highly homologous to miraculin in primary structure. I constructed its high expression system in Escherichia coli and confirmed purification method. Using the purified vvMLP, I solved crystal structure of vvMLP. Our results revealed that vvMLP exists as monomer both in the solution and in the crystal. I introduced several mutation to vvMLP to make dimer vvMLP, since dimerization is mandatory for miraculin to have taste-modifying activity. In all the mutants, most of the protein became insoluble in E. coli, but it became more soluble when some chaperon protiens were co-expressed. Soluble mutants were subjected to sensory test, but none of them was shown to have taste-modifying activity.

Free Research Field

構造生物学

Academic Significance and Societal Importance of the Research Achievements

味覚修飾活性をもつミラクリンの組換えタンパク質の大量生産は難しく、機能解析が進んでいない。本研究では、ミラクリンと60%近い配列が一致するブドウ由来ミラクリン類似タンパク質vvMLPの立体構造を明らかにした。単量体として存在するvvMLPにミラクリン型アミノ酸残基を挿入し二量体化に成功したが、この変異体は味覚修飾活性を有さなかった。大腸菌での可溶性ミラクリン生産にも成功したが、味覚修飾活性は確認されなかった。これらの結果はこれまでの味覚修飾タンパク質の研究結果と異なっており、ミラクリンの味覚修飾活性に糖鎖が重要な役割を果たす可能性を示唆し、今後の研究に一石を投じるものである。