ORIGINAL RESEARCH PAPER
Polyproline II structure is critical for the enzyme protective
function of soybean Em (LEA1) conserved domains
Yongdong Zou
•
Ruisha Hong
•
Shuwen He
•
Guobao Liu
•
Zebo Huang
•
Yizhi Zheng
Received: 6 February 2011 / Accepted: 18 March 2011 / Published online: 1 April 2011
Ó Springer Science+Business Media B.V. 2011
Abstract Group 1 late embryogenesis-abundant
(LEA1) proteins protect enzyme activity from dehy-
dration and are structurally conserved with three
different 20 amino acid motifs in the N-terminal,
middle and C-terminal domains. Three soybean Em
(LEA1) domain peptides (Em-N, Em-2M and Em-C)
covering these respective motifs were constructed
and had differential protective ability on lactate
dehydrogenase against freeze–thaw: Em-C [ Em-
2M [ Em-N. CD spectroscopy revealed that Em-
2M and Em-C contained both polyproline II (PII)
helical structure and a-helix, while Em-N had a high
potential to form a-helix but did not contain PII
structure. The PII helical structure between the third
and fifth glycine in the middle motif was shown,
through site mutation, to be critical for the enzyme
protective function of soybean Em (LEA1) conserved
domain under freezing stress.
Keywords Domain peptide Á Enzyme protection Á
a-helix Á LEA1 protein Á Polyproline II structure
Introduction
Late embryogenesis-abundant (LEA) proteins are
linked to dehydration tolerance and at least seven
groups of LEA proteins have been defined by virtue
of structural features and conserved motifs. Group 1
LEA (LEA1) proteins are extremely hydrophilic and
highly conserved with a 20 amino acid (a.a.) motif in
the middle and another two in the N- and C-terminal
domains (M-, N- and C-motif, respectively) (Batta-
glia et al. 2008). LEA1 proteins can protect lactate
dehydrogenase (LDH) and citrate synthetase from
inactivation by freezing or drying in vitro (Goyal
et al. 2005; Gilles et al. 2007).
LEA1 proteins in solution contain abundant random
coils and have no defined secondary or tertiary
structure, but may become more structured upon
drying or induction by a-helix promoters (Boudet
et al. 2006; Shih et al. 2010). The a-helical structure is
important for the protective function of LEA1 protein
on LDH activity from drying (Gilles et al. 2007). On
the other hand, LEA1 proteins contain polyproline II
Electronic supplementary material The online version of
this article (doi:10.1007/s10529-011-0602-z) contains
supplementary material, which is available to authorized users.
Y. Zou
Institute of Genetics and Cytology,
School of Life Sciences, Northeast Normal University,
Changchun 130024, China
Y. Zou Á R. Hong Á S. He Á G. Liu Á Y. Zheng (&)
Shenzhen Key Laboratory of Microbiology and Gene
Engineering, College of Life Sciences, Shenzhen
University, Shenzhen 518060, China
e-mail: yzzheng@szu.edu.cn
Z. Huang
School of Pharmaceutical Sciences and Research Center
of Food and Drug Evaluation, Wuhan University,
Wuhan 430071, China
123
Biotechnol Lett (2011) 33:1667–1673
DOI 10.1007/s10529-011-0602-z