分子監護子對於摺疊新合成的蛋白、組合多個次結構與在逆境下穩定蛋白的非摺疊態都扮演著極重要角色。許多原核與真核生物的分子監護子，當初是以熱休克蛋白 (Hsps) 形式被發現。這些Hsps依據不同的分子量來分類，其基因家族分布在質體、粒腺體、細胞質跟內質網。Hsp70s/Hsc70s經由親脂性與其受質結合，基因表現則由啟動子序列中的
熱休克反應要素 (HSE) 與熱休克轉錄因子 (HSF) 蛋白來調控。Hsc70的蛋白結構包含44-kDa保守性極高的ATPase區域，保守性較低的18-kDa蛋白結合區與C端10-kDa的變異區。DnaJ/Hsp40會加速ATP水解速率而提高Hsc70的ATPase活性。Hop/p60則跟Hsp70與Hsp90之間的物理連結有關。這兩群輔蛋白是非競爭性的跟Hsc70末端10-kDa區域結合來作用。Bag-1/GrpE能刺激ADP與ATP間的交換，Hip/p48卻能穩定在ADP結合態下的Hsc70，這兩組功能拮抗的蛋白則作用在Hsc70的ATPase區域上。

番茄的種子吸水後，有兩群的Hsc70s表現，但只有一群Hsc70存在葉子，代表不同發育時期，或者不同的逆境處理都可能造成不同的Hsc70s消長。我們利用pET蛋白表現系統，構築成含有番茄Hsc70不同區域片段的重組蛋白，以研究植物和動物Hsc70s與受質結合的差異。我們也利用病毒表現 (phage display)來篩選跟Hsc70結合的片段。在選出的16個片段，其中HPMSRPR佔有37.5%。植物Hsc70的10-kDa區域帶有較多的親水性胺基酸，而動物Hsc70帶有較多親脂性的胺基酸。

Molecular chaperones are important in folding newly synthesized polypeptides, assembly of multi-subunit structure and stabilization of proteins unfolded during cellular stresses. Many chaperones were discovered as heat shock proteins (Hsps) from prokaryotes to eukaryotes and classified into groups by the different molecular weight. Hsp70s/Hsc70s bind theirs substrates through hydrophobic interactions and were encoded by gene families in the plastid, mitochondrion, cytoplasm and endoplastic reticulum. The expression of the heat-shock genes is regulated by cis-regulatory promoter elements (HSEs) and trans-active heat shock transcription factors (HSFs). Hsp70s/Hsc70s consist of a highly conserved N-terminal 44-kDa ATPase domain, a less conserved 18-kDa peptide-binding domain and a C-terminal 10-kDa variable domain. DnaJ/Hsp40 stimulates the ATPase activity by accelerating the rate of ATP hydrolysis. Hop/p60 provides a physical link between Hsp70 and Hsp90. These two cofactors bind to the 10-kDa C-terminal domain of Hsc70 in a noncompetitive manner. Bag-1/GrpE is the nucleotide release factor stimulating exchange of ADP for ATP. On the other hand, Hip/p48 stabilizes the ADP bound form by inhibiting the release of nucleotide and has been shown to compete the function of Bag-1 in binding to the ATPase domain.
Two bands of tomato Hsc70s were detected in seeds, but only one band was detected in leaves. Expression of different Hsc70s at different developmental stages or under stress may be related to the Hsc70s functions and regulation. PET chimeras were constructed to obtain different subdomains of tomato Hsc70s for studying differences of substrate binding in plants and animals. We also performed phage-display selections to screen the peptides bound to Lehsc70-1 30-kDa protein. The observed frequency of HPMSRPR was 37.5% in the 16 selected peptides. A animal Hsc70s contain more hydrophobic residues and plant Hsc70s contain more hydrophilic residues in 10-kDa domains of Hsc70.

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