<Page>

                                                                     EXHIBIT 4.3

                         PARTNERSHIP UNIT DESIGNATION OF
              9.125% SERIES G CUMULATIVE REDEEMABLE PREFERRED UNITS

     The following partnership unit designation (this "PARTNERSHIP UNIT
DESIGNATION") is a statement of the designations, qualifications, special or
relative rights and privileges of the 9.125% Series G Cumulative Redeemable
Preferred Units of Keystone Operating Partnership, L.P. (the "PARTNERSHIP").
Capitalized terms used but not otherwise defined in this Partnership Unit
Designation shall have the same meanings ascribed to them in the Partnership's
Amended and Restated Agreement of Limited Partnership, dated as of October 13,
1999, and any amendments thereto (collectively, the "PARTNERSHIP AGREEMENT").

Section 1.  NUMBER OF PREFERRED UNITS AND DESIGNATION. A series of
Partnership Units, designated as 9.125% Series G Cumulative Redeemable Preferred
Units (the "SERIES G PREFERRED UNITS"), is hereby established. The number of
Series G Preferred Units shall be 2,760,000, which number may be decreased (but
not below the number thereof then outstanding) from time to time by the General
Partner.

Section 2.  DEFINITIONS.

"ARTICLES SUPPLEMENTARY FOR THE SERIES D PREFERRED STOCK" shall mean the
Articles Supplementary Establishing and Fixing the Rights and Preferences of a
Series of Shares of Preferred Stock as 9.125% Series D Cumulative Redeemable
Preferred.

"BUSINESS DAY" shall mean any day, other than a Saturday or Sunday, that is
neither a legal holiday nor a day on which banking institutions in The City of
New York are authorized or required by law, regulation or executive order to
close.

"GENERAL PARTNER" shall mean Keystone Property Trust, a Maryland statutory real
estate investment trust and the general partner of the Partnership.

"OP UNITS" shall mean any class or series of units of limited partnership
interest in the Partnership that are not Preferred Units.

"PREFERRED UNITS" shall mean any units issued by the Partnership that may be
issued in one or more series or classes, having such rights, possible duties and
preferences as may be determined by the General Partner in its sole and absolute
discretion.

"SERIES D PREFERRED STOCK" shall mean the 9.125% Series D Cumulative Redeemable
Preferred Stock of the General Partner, par value $.001 per share.

"SERIES C PREFERRED UNITS" shall mean the Series C Convertible Preferred Units
of the Partnership.

"SERIES D PREFERRED UNITS" shall mean the Series D Convertible Preferred Units
of the Partnership.

"SERIES F PREFERRED UNITS" shall mean the Series F Convertible Preferred Units
of the Partnership.

<Page>

Section 3.  DISTRIBUTIONS.

            (a)  Subject to the rights of holders of any classes or series of
units of partnership interest of the Partnership senior to the Series G
Preferred Units as to the payment of distributions, the General Partner, in its
capacity as the holder of the then outstanding Series G Preferred Units, shall
be entitled to receive, when, as and if authorized by the General Partner,
cumulative quarterly preferential cash distributions in an amount per unit equal
to 9.125% of the $25.00 liquidation preference per annum (equivalent to a fixed
annual amount of $2.28125 per unit). Distributions on the Series G Preferred
Units shall accrue and be fully cumulative from the date of original issuance
and shall be payable quarterly when, as and if authorized by the General
Partner, in equal amounts in arrears on the last calendar day of each January,
April, July and October or, if not a Business Day, the next succeeding Business
Day (each, a "SERIES G PREFERRED UNIT DISTRIBUTION PAYMENT DATE"). Any
distribution (including the initial distribution) payable on the Series G
Preferred Units for any partial distribution period shall be prorated and
computed on the basis of a 360-day year consisting of twelve 30-day months. The
term "distribution period" shall mean the period from the date of original
issuance and ending on and including the next Series G Preferred Unit
Distribution Payment Date, and each subsequent period from but excluding such
Series G Preferred Unit Distribution Payment Date and ending on and including
the next following Series G Preferred Unit Distribution Payment Date.

            (b)  No distribution on the Series G Preferred Units shall be
authorized by the General Partner or declared or paid or set apart for payment
by the Partnership at such time as the terms and provisions of any agreement of
the General Partner or the Partnership, including any agreement relating to its
indebtedness, prohibits such authorization, declaration, payment or setting
apart for payment or provides that such authorization, declaration, payment or
setting apart for payment would constitute a breach thereof, or a default
thereunder, or if such authorization, declaration, payment or setting apart for
payment shall be restricted or prohibited by law. No interest, or sum of money
in lieu of interest, shall be payable in respect of any distribution payment or
payments on the Series G Preferred Units which may be in arrears.

            Notwithstanding the foregoing, distributions with respect to the
Series G Preferred Units shall accumulate whether or not any of the foregoing
restrictions exist, whether or not there is sufficient available cash for the
payment thereof and whether or not such distributions are authorized.
Accumulated but unpaid distributions on Series G Preferred Units shall not bear
interest and holders of the Series G Preferred Units shall not be entitled to
any distributions in excess of full cumulative distributions. Any distribution
payment made on the Series G Preferred Units shall first be credited against the
earliest accumulated but unpaid distribution due with respect to such units
which remains payable.

            (c)  Except as provided in Section 3(d) below, unless full
cumulative distributions have been or contemporaneously are authorized, declared
and paid or authorized, declared and a sum sufficient for the payment thereof
set apart for such payment on the Series G Preferred Units for all past
distribution periods and the then current distribution period, no distributions
(other than in any classes or series of units of partnership interest of the
Partnership ranking junior to the Series G Preferred Units as to the payment of
dividends and the distribution of assets upon any liquidation, dissolution or
winding up of the Partnership) shall be authorized, declared or paid or set
apart for payment nor shall any other distribution be authorized, declared or
made upon any classes or series of units of partnership interests ranking, as to
the payment of distributions or the distribution of assets upon any liquidation,
dissolution or winding up of the Partnership, junior to or on a parity with the
Series G Preferred Units for any period, nor shall any classes or series of
units of partnership interest of the Partnership ranking junior to or on a
parity with the Series G Preferred Units as to the payment of distributions or
the distribution of assets upon any liquidation, dissolution or winding up of
the Partnership, be redeemed, purchased or otherwise

                                        2
<Page>

acquired for any consideration (or any monies be paid to or made available for a
sinking fund for the redemption of any such classes or series of units of
partnership interest) by the Partnership (except by conversion into or exchange
for any classes or series of units of partnership interest ranking junior to the
Series G Preferred Units as to the payment of distributions and the distribution
of assets upon any liquidation, dissolution or winding up of the Partnership).

            (d)  When distributions are not paid in full (or a sum sufficient
for such full payment is not so set apart) upon the Series G Preferred Units and
any other classes or series of units of partnership interest ranking on a parity
as to the payment of distributions with the Series G Preferred Units, all
distributions authorized and declared upon the Series G Preferred Units and any
other classes or series of units of partnership interest ranking on a parity as
to the payment of distributions with the Series G Preferred Units shall be
declared pro rata so that the amount of distributions authorized and declared
per Series G Preferred Unit and such other classes or series of units of
partnership interest shall in all cases bear to each other the same ratio that
accumulated distributions per each Series G Preferred Unit and such other
classes or series of units of partnership interest (which shall not include any
accumulation in respect of unpaid distributions for prior distribution periods
if such other any classes or series of units of partnership interest do not have
a cumulative distribution) bear to each other.

            (e)  Holders of Series G Preferred Units shall not be entitled to
any distribution, whether payable in cash, property or any classes or series of
units of partnership interest issued by the Partnership, in excess of full
cumulative distributions on the Series G Preferred Units as described above.
Accrued but unpaid distributions on the Series G Preferred Units will accumulate
as of the Series G Preferred Units Distribution Payment Date on which they first
become payable.

Section 4.  LIQUIDATION PREFERENCE.

            (a)  In the event of any voluntary or involuntary liquidation,
dissolution or winding up of the Partnership, the General Partner, in its
capacity as holder of the Series G Preferred Units, shall be entitled to receive
out of the assets of the Partnership available for distribution to the Partners
pursuant to Article VIII of the Partnership Agreement a liquidation preference
of $25.00 per Series G Preferred Unit, plus an amount equal to any accumulated
and unpaid distributions (whether or not earned or authorized) to the date of
payment, before any distribution of assets is made to holders of any OP Units or
any other class or series of units of partnership interest issued by the
Partnership that rank junior to the Series G Preferred Units as to the
distribution of assets upon the liquidation, dissolution or winding up of the
Partnership, but subject to the preferential rights of the holders of any
classes or series of units of partnership interest ranking senior to the Series
G Preferred Units as to the distribution of assets upon the liquidation,
dissolution or winding up of the Partnership.

            (b)  If upon any such voluntary or involuntary liquidation,
dissolution or winding up of the Partnership, the assets of the Partnership
legally available for distribution to its Partners are insufficient to make such
full payment to the General Partner, in its capacity as the holder of the Series
G Preferred Units and the corresponding amounts payable on all outstanding units
of other classes or series of units of partnership interest of the Partnership
ranking on a parity with the Series G Preferred Units as to the distribution of
assets upon the liquidation, dissolution or winding up of the Partnership, then
the General Partner, in its capacity as the holder of the Series G Preferred
Units, and all other holders of such classes or series of units of partnership
interest of the Partnership shall share ratably in any such distribution of
assets in proportion to the full liquidating distributions (including, if
applicable, accumulated and unpaid distributions) to which they would otherwise
be respectively entitled.

                                        3
<Page>

            (c)  After payment of the full amount of the liquidating
distributions to which it is entitled, the General Partner, in its capacity as
the holder of the Series G Preferred Units, shall have no right or claim to any
of the remaining assets of the Partnership.

            (d)  None of a consolidation or merger of the Partnership with or
into another entity, a merger of another entity with or into the Partnership, a
statutory unit exchange by the Partnership or a sale, lease or conveyance of all
or substantially all of the Partnership's property or business shall be
considered a liquidation, dissolution or winding up of the Partnership.

Section 5.  REDEMPTION. In connection with the redemption by the General Partner
of any of shares of Series D Preferred Stock in accordance with the provisions
of the Articles Supplementary of the Series D Preferred Stock, the Partnership
shall provide cash to the General Partner for such purpose which shall be equal
to the redemption price (as set forth in the Articles Supplementary of the
Series D Preferred Stock), plus all distributions accumulated and unpaid to the
Redemption Date (as defined in the Articles Supplementary of the Series D
Preferred Stock) (or, as applicable, the accumulated and unpaid distribution
payable pursuant to Section 6(b)(iv) of the Articles Supplementary of the Series
D Preferred Stock), and one Series G Preferred Unit shall be concurrently
redeemed with respect to each share of Series D Preferred Stock so redeemed by
the General Partner. From and after the applicable Redemption Date (as defined
in the Articles Supplementary of the Series D Preferred Stock), the Series G
Preferred Units so redeemed shall no longer be outstanding and all rights
hereunder, to distributions or otherwise, with respect to such Series G
Preferred Units shall cease. Any Series G Preferred Units so redeemed may be
reissued to the General Partner at such time as the General Partner reissues a
corresponding number of shares of Series D Preferred Stock so redeemed or
repurchased, in exchange for the contribution by the General Partner to the
Partnership of the proceeds from such reissuance of shares of Series D Preferred
Stock.

Section 6.  CONVERSION.  The Series G Preferred Units are not convertible into
or exchangeable for any other property or securities of the Partnership.

Section 7.  RANKING. The Series G Preferred Units, with respect to rights to the
payment of dividends and the distribution of assets upon the liquidation,
dissolution or winding up of the Partnership, rank (a) senior to all OP Units
and any other class or series of units of partnership interest issued by the
Partnership the terms of which specifically provide that such class or series of
units of partnership interest rank junior to the Series G Preferred Units; (b)
on parity with the Series C Preferred Units, the Series D Preferred Units, the
Series F Preferred Units and any other class or series of units of partnership
interest issued by the Partnership the terms of which specifically provide that
such class or series of units of partnership interest rank on a parity with the
Series G Preferred Units; and (c) junior to any class or series of units of
partnership interest issued by the Partnership the terms of which specifically
provide that such class or series of units of partnership interest rank senior
to the Series G Preferred Units.

Section 8.  VOTING. Except as required by applicable law, the General Partner,
in its capacity as the holder of the Series G Preferred Units, shall have no
voting rights.

Section 9.  RESTRICTIONS ON OWNERSHIP. The Series G Preferred Units shall be
owned and held solely by the General Partner.

Section 10. ALLOCATIONS. Allocations of the Partnership's items of income, gain,
loss and deduction shall be allocated to the General Partner, in its capacity as
the holder of the Series G Preferred Units, in accordance with Article V of the
Partnership Agreement.

                                        4
<Page>

     IN WITNESS WHEREOF, this Partnership Unit Designation has been duly
executed by the General Partner on behalf of the Partnership as of the day and
year set forth below.


     DATED: February 14, 2003          GENERAL PARTNER

                                       KEYSTONE PROPERTY TRUST


                                       By: /s/ Timothy E. McKenna
                                          --------------------------------------
                                          Name:  Timothy E. McKenna
                                          Title: Senior Vice President