수송 결함을 지난 리보스 결합 전구체 단백질, 복귀 전구체 단백질 및 숙성단백질을 부분 또는 순수 정제하고 이들이 기질에 결합하는 것을 조사하여 대량생산된 리보스 결합 단백질들이 native conformation을 유지하고 있음을 확인하였다. 따라서 이들 단백질을 수송 능력과 구조 사이의 관계를 알아보기 위한 in vitro 분석에 사용하였다. 이들 단백질에 리보스가 결합하는 정도의 비교, circular dichroism 의 측정 및 proteinase K에 대한 내성을 조사한 결과 steady state에서 이들 단백질 사이에 현저한 구조적 차이가 없음을 밝혔다.
Three alleles of rbsB gene including export defective mutant were cloned for overproduction of proteins. Five different species of precursor and mature ribose-binding proteins were purified to homogeneity. The purified proteins were subjected to amino acid sequencing. The results confirmed the amino acid changes deduced from the DNA sequencing (Park et al., 1988a). Attempts were made to establish a correlation between export competency and conformation of the proteins by studies in vitro. In this regard, ligand binding ability, circular dichroism, and the sensitivity to the degradation by a protease were compared. However, there was no drastic conformational difference among these proteins in steady states. This results, in other aspect, implied that the proteins purified from the overproduced proteins are in native conformation and allowed further analysis for studying the mechanism of protein export in vitro.
